can psychedelic drugs attenuate age-related changes in cognition and affect (pdf)
pdf version

bookmarks

search on psilosophy:  
   

Can Psychedelic Drugs Attenuate Age-Related Changes in Cognition and Affect

by

Jacob S. Aday1 & Emily K. Bloesch1 & Christopher C. Davoli1

Received: 30 May 2019 / Accepted: 20 August 2019

Journal of Cognitive Enhancement
DOI: 10.1007/s41465-019-00151-6

© Authors 2019

1 Department of Psychology, Central Michigan University, Mount Pleasant, MI 48858, USA

Corresponding author:
Jacob S. Aday
aday1js@cmich.edu

Table of Contents:
Abstract
Introduction
Cognitive Parallels
Affective Parallels
Potential Mechanisms
Safety
Future Directions
Conclusion
Compliance with Ethical Standards
References

Abstract

Older adulthood can be characterized by various cognitive and affective changes. In general, older adults show declines in creativity and executive functioning. They also score lower in openness to experience, empathy, and many suffer from a paucity of meaningful experiences. Further, depression, pessimism, and suicide can be major concerns for this population. Although currently there are few interventions that can effectively address these changes, recent findings from psychedelic science suggest myriad parallels between the effects of these drugs and the cognitive/affective shifts seen in older adulthood. Studies have shown that psychedelics are associated with enhanced creativity and executive functioning. They can also lead to increases in openness and empathy, and induce personally meaningful experiences. Lastly, psychedelics' efficacy for treating mood disorders and their role in palliative care are rapidly growing areas of scientific research. In this article, we analyze findings from contemporary psychedelic studies and integrate them with research on cognitive/affective changes in older adulthood to assess whether these drugs have potential to be incorporated into older adult research. We also assess the intuitive follow-up questions of potential mechanisms of action and safety concerns. Findings indicate that psychedelics have effects on a number of cognitive/affective processes that are altered in older adulthood, and are relatively safe when used with professional preparation and supervision. Increased neuroplasticity, neurogenesis, connectedness, and mystical experiences have been argued to underlie cognitive/affective changes. However, further research is needed to overcome current experimental limitations such as generalizability, unstandardized dosages, inadequate controls, and self-selection/experimenter biases.

Keywords Psychedelics, Cognition, Affect, Aging, Well-being

Introduction

A number of cognitive and affective changes have been documented in older adulthood, which is typically conceptualized as beginning in one's 60s (Salthouse 2009). These changes can include declines in creativity and generating novel ideas (Price and Tinker 2014), impaired executive functioning (Baudouin et al. 2019), decreased openness to experience (Donnellan and Lucas 2008), and decreased empathy (Grühn et al. 2008). Further, although depression scores generally drop after early adulthood, late-life depression is one of the most common causes of emotional suffering in older adults (Blazer 2003; Wang and Blazer 2015), and the elderly have higher rates of suicide than younger adults (De Leo and Meneghel 2001; Kumar et al. 2015). These changes in negative affect may be due in part to a lack of meaningful experiences: Baum (1988) found that when elderly persons were asked to recount their most meaningful life experiences, none of the 50 participants reported an event after the age of 40. Lastly, the number of neurons in the brain decreases in older age as neurons that die off are not replaced as efficiently (Galvan and Jin 2007). Because neurogenesis is thought to play a major role in age-related cognitive and affective deficits, interventions which stimulate neurogenesis may build-up a cognitive reserve which could help reduce the intellectual and emotional burdens in late-life (Xu et al. 2015).

This is not to say that aging is inherently negative as many older adults experience high life satisfaction and emotional stability (Charles and Carstensen 2010; Scheibe and Carstensen 2010). Yet, risk factors for cognitive and affective decline can have a cumulative effect across individuals' lifespans ultimately leading to impairment (Camacho et al. 1993; Zeki Al Hazzouri et al. 2014). Addressing these risk factors can stave off cognitive decline (Mossello et al. 2008) and identifying holistic treatments which target multiple risk factors could facilitate healthy aging (Cesari et al. 2013). Thus, while older adults show changes in cognition and affect at the group level, many variables can exert compensatory effects on individual trajectories (Smith 2016).

Psychedelic drugs such as lysergic acid diethylamide-25 (LSD), psilocybin, and ayahuasca have been shown to induce alterations in cognition and affect that run counter to the changes seen in older adulthood. Research into psychedelic drugs blossomed in the mid-twentieth century but was put to a halt in the late 1960s as the War on Drugs emerged (Aday et al. 2019). However, the last 10-15 years has seen a renaissance of psychedelic research, and their public stigma seems to be waning as evidenced by recent positive pieces in mainstream media outlets (e.g., the New York Times Carroll 2017; Wall Street Journal Pollan 2018; Business Insider Brodwin 2018) and successful decriminalization efforts in parts of the USA (Aday et al. 2018, A watershed year for psychedelic science, unpublished). There are many parallels between the findings from these new studies and psychological changes in older adulthood. First, psychedelics have been shown to increase divergent (Kuypers et al. 2016) and convergent creativity (Uthaug et al. 2018). They can also lead to long-lasting increases in the personality trait of openness (MacLean et al. 2011) as well as increasing empathy (Pokorny et al. 2017). Psychedelic-assisted psychotherapy has been shown to have promising effects on depression (Griffiths et al. 2016; Ross et al. 2016). Relatedly, psychedelic use is associated with decreased psychological distress and suicidality (Hendricks et al. 2015). Psychedelics may also address the lack of meaningful experiences in older adulthood: in one study, two thirds of participants reported their psychedelic session as being one of the top five most meaningful experiences of their life (Griffiths et al. 2006). Their role in palliative care is also a rapidly growing area of study (Shelton and Hendricks 2016). Lastly, there is emerging evidence in animal models that psychedelics can stimulate neurogenesis (Catlow et al. 2016; Lima da Cruz et al. 2018; Morales-García et al. 2017) and neuroplasticity (Ly et al. 2018), which may be key mechanisms facilitating improvements. Altogether, the reviewed literature suggests many parallels between cognitive/affective changes in older adulthood and the effects of psychedelic drugs. In this paper, we analyze recent findings in psychedelic research and synthesize them with studies on cognitive and affective changes in late-life to determine whether these substances have potential to be incorporated into older adult research.

Cognitive Parallels

Relative to younger individuals, older adults suffer deficits in cognition in areas such as memory and attention (Mok et al. 2016). Older age can also be associated with declines in creativity and executive functioning, and these changes in cognition may impair one's quality of life (Baudouin et al. 2019). There is growing evidence that psychedelic drug use is associated with improved creativity and executive functioning, suggesting that these drugs may have potential cognitive benefits for older adults.

Anecdotal reports about psychedelics' potential for improving creativity date back to the first era of psychedelic research during the mid-twentieth century and were espoused by diverse figures - from Aldous Huxley to Francis Crick to the Beatles (Goodden 2017; Sessa 2008). Researchers soon picked up on the connection between psychedelics and creativity as demonstrated by myriad articles published during this period (e.g., Harman et al. 1966; McGlothlin, Cohen, & McGlothlin et al. 1967; Zegans et al. 1967; see Sessa 2008, for a review). Today, researchers are revisiting psychedelic drugs' potential for improving creativity. Kuypers et al. (2016) found that while under the influence of ayahuasca, participants had increased divergent, but decreased convergent, creativity compared to their pre-ayahuasca session. These results contrast with another study which found improved convergent creativity after ayahuasca ingestion that lasted at least 4 weeks (Uthaug et al. 2018). In another study looking at non-acute effects, participants who partook in an ayahuasca retreat demonstrated enhanced creative expression relative to a control group similar in sex and age (Frecska et al. 2012). Finally, Prochazkova et al. (2018) found that when on "microdoses" of psychedelics (i.e., ~ 1/10th of a standard dose), participants had improved divergent and convergent creativity; however, the results must be interpreted with caution as participants were self-selected and not blind to conditions. It is also important to keep in mind that many of the aforementioned studies lacked adequate control groups given that it is difficult to blind participants between a consciousness-altering drug and placebo (Hendy 2018). Additionally, it is unclear if these effects generalize to older adulthood because no studies to date have directly assessed psychedelics' effects on creativity in this population. The inconclusive results in the literature thus far can most likely be attributed to differences in timing (i.e., acute vs. non-acute effects) and dosage. However, the wealth of anecdotal reports and promising findings from preliminary empirical research suggest a relationship between psychedelic use and creativity. Thus, although more research is needed, psychedelic drugs may have the potential to compensate for declines in creativity in older age and stimulate new ideas or styles of thinking (Uthaug et al. 2018).

Psychedelics may also have effects on age-related cognitive changes in areas such as executive functioning. In a study examining regular ayahuasca users with controls who were similar in sex, age, education, and income, Buoso and colleagues (Bouso et al. 2012) found that the users performed better on the Stroop task, the Wisconsin Card Sorting Test (WCST), the Letter-Number Sequencing task, and the Frontal Systems Behavior Scale. These findings suggest that psychedelic use is associated with increased working memory and set-shifting, which are two key components of executive functioning. Consistent with these results, another study found greater working memory performance in psychedelic drug users and a trend towards improved scores on the WCST relative to a control group that was matched for sex, age, income, and verbal and fluid intelligence quotient (IQ) scores (Bouso et al. 2015). Given the correlational nature of these studies, future experimental research is needed to delineate causation as well as test whether these improvements are maintained as individuals age. However, given that psychedelics stimulate plasticity (Ly et al. 2018) and enhanced plasticity has been shown to improve executive functioning (Selemon 2013), there is reason to expect that psychedelics have a causal effect on executive function. These results, in tandem with studies on psychedelics and creativity, suggest that psychedelics may be able to attenuate some of the cognitive changes related to older adulthood.

Affective Parallels

A striking parallel between psychedelic drugs and older adulthood regards their connections with affective processing. As previously mentioned, late-life can be associated with a number of affective shifts, including changes in openness to experience (Donnellan and Lucas 2008), empathy (Grühn et al. 2008), pessimism (Chang et al. 2013), rates of depression/suicide (De Leo and Meneghel 2001; Kumar et al. 2015; Wang and Blazer 2015), and meaningful experiences (Baum 1988). These affective changes can have considerable implications for overall well-being and quality of life in the elderly (Chang et al. 2013). For instance, treating depression decreases the severity of cognitive decline in the elderly (Mossello et al. 2008) and increased openness to experience is related to successful aging (Gregory et al. 2010). For those wanting to counter affective changes documented in older adulthood, evidence is mounting that psychedelics induce several opposing effects.

One affective change that has been consistently related to psychedelics is increased openness to experience. MacLean et al. (2011) found that participants reported increased openness after a high-dose psilocybin session relative to a control methlyphenidate session, and these changes were maintained for at least 1 year. Although this study was limited by a selection bias (i.e., recruitment materials advertised that participants would be taking psilocybin), subsequent studies have replicated increased openness after psychedelic use (Bouso et al. 2018; Erritzoe et al. 2018; Lebedev et al. 2016). Studies in this area could also be tainted by experimenter bias: given the stigma historically associated with these drugs, potentially only researchers with deep intrinsic interest in psychedelics would be willing to risk their professional credibility and resources by entering the field. This could bias the type of questions researchers study with the drugs (i.e., there could be a lack of studies on negative outcomes related to psychedelics). Lastly, it is possible that participants showed increased openness because they were on an illicit drug rather than because of psilocybin per se. That is, perhaps after having an enjoyable experience with something highly stigmatized, individuals may wonder what other stigmatized/disconcerting activities they should also be open to. Changes in openness may nevertheless have exponential downstream effects on other cognitive and affective outcomes, such as creativity (Silvia et al. 2009). Further, psychedelic use has been shown to increase emotional empathy (Pokorny et al. 2017), which may also be related to changes in openness. Speculatively, it seems that increased openness to experience could also increase the number of meaningful experiences in older adulthood. In any case, the changes in openness induced by psychedelics seem to run counter to the changes seen in late-life.

Perhaps the most rapidly growing area of psychedelic research is in their treatment for affective disorders like depression (Griffiths et al. 2016; Carhart-Harris et al. 2016; Ross et al. 2016; Uthaug et al. 2018). Indeed, in the USA, the FDA recently designated psilocybin to "breakthrough therapy" status for treatment-resistant depression (Bauer 2019), which should expedite future research in this area. Given the wide variety of negative outcomes associated with depression, this research could have important implications for older adults. In one stark example, Griffiths et al. (2016) found that following psilocybin-assisted psychotherapy, 80% of their depressed patients showed a reduction in symptoms that were maintained for at least 6 months after their sessions. Ross et al. (2016) concurrently found similar findings (i.e., 60-80% of patients had a reduction in symptoms 6.5 months after their sessions) in a rigorous double-blind, placebo-controlled, and crossover trial of cancer patients experiencing end-of-life distress. The findings from the Griffiths and Ross experiments are particularly pertinent to older adults given the average age in each of their studies was 56 years old. Further, while older adults are generally more pessimistic (Chang et al. 2013), psychedelic therapy has been shown to reduce pessimism and these changes are related to therapeutic outcomes with depression (Lyons and Carhart-Harris 2018). Heightened emotion regulation has also been linked with healthy aging (Suri and Gross 2012) and is increased in male psychedelic users compared to male non-users (Thiessen et al. 2018). Lastly, correlational research shows a negative relationship between psychedelic use and psychological distress and suicidal behaviors (Hendricks et al. 2015). Altogether, there is growing evidence that these drugs induce changes in emotional processing that oppose many changes seen in late-life.

Another affective connection between psychedelics and older adults regards meaningful experiences. As previously mentioned, the elderly report a paucity of meaningful events in later life (Baum 1988). Intuitively, a lack of meaningful experiences may be a contributing factor in pessimism, late-life depression, and increased rates of suicide in the elderly (Heisel and Flett 2008). Indeed, low meaning in life has been linked with increased suicide ideation (Heisel and Flett 2008), and interventions aimed at increasing meaning improve wellbeing in the elderly (Breitbart et al. 2015). Recent findings from psychedelic science suggest that psychedelic drugs may be able to treat this lack of meaningful experiences. In what is perhaps the seminal psychedelic study of the twenty-first century so far, Griffiths et al. (2006) found in their double-blind experiment that two thirds of their participants rated their psilocybin session as being one of the top five most meaningful experiences in their life - comparable to events like the birth of a child or death of a parent. Further, 38% said it was one of their top five most spiritually significant experiences, and 79% of participants in this study rated that the experience improved their sense of well-being or life satisfaction "moderately" or "very much." The results illustrate that psychedelic drugs can induce experiences that are incredibly meaningful, even spiritual; this could have monumental implications for older adults suffering from a lack of meaningful experiences.

Relatedly, psychedelics' effects on end-of-life distress and palliative care is another area of current study (Kelmendi et al. 2016; Shelton and Hendricks 2016). Although this line of research was predated by similar studies in the first era of psychedelic research (e.g., Cohen 1965; Fisher 1970; Grof et al. 1973), improved experimental methodology has greatly advanced our understanding of the role psychedelics can play at the end-of-life. The first study in this area during the current era of psychedelic research was a double-blind, placebo-controlled pilot study which showed modest improvements in measures of well-being (Grob et al. 2011). Though limited by a small sample and relatively low dosage of psilocybin, the study was important in reestablishing proof-of-concept and safety protocols. More rigorous studies followed in 2016 as both Griffiths et al. and Ross et al. found robust decreases in measures of end-of-life distress. Finally, another study found that, in a dose-dependent manner, psilocybin treatment led to increases in life satisfaction, positive attitudes about life, and spirituality (Griffiths et al. 2011) - which can be critical factors in healthy aging that buffer against emotional distress (Grob et al. 2013).

Potential Mechanisms

Given the sheer number of cognitive and affective changes that have been related to psychedelics, they are each likely supported by distinct and overlapping mechanisms. In this section, we touch on the potential mechanisms underlying the previously mentioned alterations in cognition and affect associated with these substances.

Psychedelic drugs exert their acute effects predominantly through serotonin 5-HT2A receptors (Preller et al. 2017; Vollenweider et al. 1998). These receptors are widely distributed in the cortex, explaining the diverse effects of psychedelics and play a key role in memory and cognition (Zhang and Stackman Jr 2015). In animal studies, 5-HT2A activation has led to increased cognitive flexibility as well as associative learning (Carhart-Harris et al. 2014). Therefore, psychedelics may also affect cognitive flexibility, which could explain their effects on creativity, executive functioning (i.e., set-shifting), openness, and depression. Indeed, Jungaberle et al. (2018) noted that cognitive flexibility is generally heightened in psychedelic states. Carhart-Harris et al. (2014) proposed an exhaustive model of the effects of psychedelic drugs that begins at the 5-HT2A receptor level and builds into the desynchronization of higher-level networks in the brain (see Carhart-Harris 2018, 2019, for further discussion of the entropic brain hypothesis).

Another - more speculative - explanation for the cognitive changes related to psychedelics is increased neurogenesis and neuroplasticity (Lima da Cruz et al. 2018). Decreased neurogenesis is thought to be a key factor underlying declines in cognition in older adults as neurons that die off are not replaced as efficiently (Galvan and Jin 2007; Xu et al. 2015). Additionally, Goh and Park (2009) argued that enhanced neuroplasticity could act as a compensatory response in the aging brain, and they suggested that interventions should be identified that can stimulate plasticity. Psychedelic drugs are intriguing candidates for inducing these critical changes in the brain. Several studies in recent years have shown that administering psychedelic drugs in vitro (Catlow et al. 2013) and in vivo (Catlow et al. 2016; Lima da Cruz et al. 2018; Morales-García et al. 2017) stimulates neurogenesis. Further, a recent paper in Cell Reports demonstrated that psychedelics increased neuroplasticity and synaptogenesis (Ly et al. 2018). However, this mechanism remains uncertain until the results are replicated in human samples. Increased neurogenesis and neuroplasticity could explain some of the affective changes that have been related to psychedelics. Atrophy of prefrontal cortex neurons is thought to be a contributing factor to depression (Christoffel et al. 2011; Ly et al. 2018), and Jacobs et al. (2000) speculated that enhancing neurogenesis could aid in the recovery from depression. Given that relatively few interventions have been identified that can increase neurogenesis and plasticity, psychedelic drugs' potential in this domain is an important area of future research and this mechanism could contribute to the cognitive and affective changes (Vollenweider and Kometer 2010).

Some have argued that the increased sense of connectedness resulting from psychedelics underlies much of their therapeutic potential (Carhart-Harris et al. 2018). Individuals often report a profound sense of "oneness," ego dissolution, and a loss of a sense of self while on the drugs (Lebedev et al. 2015). Validating these anecdotal accounts, several recent studies have shown that the default mode network (DMN), which is fundamental in maintaining a sense of self, is deactivated while on psychedelics (Carhart-Harris et al. 2012; Palhano-Fontes et al. 2015; Smigielski et al. 2019). Millière et al. (2018) argue that the functional disintegration of the DMN during psychedelic states can drastically alter aspects of consciousness through transient decreases in self-referential thought and access to autobiographical information, leading to alterations in one's sense of self-identity. This shift in perspective may underlie changes in openness and empathy as individuals become less self-centered and more open to new ways of thinking. Indeed, changes in ego dissolution predicted subsequent increases in openness (Lebedev et al. 2016) as well as positive therapeutic outcomes (Griffiths et al. 2008; Ross et al. 2016). Given that depressed individuals are characterized by more self-referential cognitions and increased DMN activity (Sheline et al. 2009), these changes in one's sense of self seem to be an important mechanism underlying clinical changes associated with psychedelic drugs.

Finally, the degree to which one has a "mystical" experience while on the drugs predicts therapeutic outcomes (Garcia-Romeu et al. 2019, 2014; Griffiths et al. 2016; Roseman et al. 2018; Ross et al. 2016; Russ et al. 2019; Schmid and Liechti 2018) as well as changes in openness (MacLean et al. 2011). Mystical experiences are marked by a profound sense of meaning/sacredness, interconnectedness with others and the world, transcendence of time and space, ineffability, and a deep positive mood (Grob et al. 2013; Kelmendi et al. 2016). Deactivation of the DMN seems to be one component in having a mystical experience (Swanson 2018), which may explain their shared therapeutic outcomes. Declines in DMN activity are consistent with the decreases in self-referential processing as well as feelings of spacelessness and timelessness associated with mystical experiences (Barrett and Griffiths 2017). Griffiths et al. (2011) found that the dosage of psilocybin which yielded the highest probability of a mystical experience was also the dosage participants reported as the most personally meaningful, spiritually significant, and the session which they would most want to repeat given the opportunity. Similarly, Grob et al. (2013) argued that the mystical experience is critical in mediating psychedelic-related benefits, particularly in palliative care. They hypothesized that the patient's self-image can be "recalibrated" during this time of transcendence, such that they adopt a broader existential perspective and the concept of death is less anxiety-provoking. Psilocybin's tendency to increase a sense of continuity after death (Griffiths et al. 2011) may also be contributing to declines in end-of-life distress.

Safety

A natural concern when considering administering illicit drugs is safety. It is not recommended for seniors (or anyone) to take these substances unsupervised or without professional medical consultation. The tendency for psychedelics to induce acute increases in blood pressure, body temperature, heart rate, plasma cortisol, and epinephrine should be considered by consulting physicians (Nichols 2016). Current researchers put a strong emphasis on mentally preparing individuals for the experience, and they stress that the benefits derived from psychedelic-assisted psychotherapy sessions may not generalize to recreational psychedelic use (Honig 2019). That being said, correlational studies have shown that psychedelic use is not linked to mental health problems or suicidal behavior (Johansen and Krebs 2015), and their use is linked to reduced psychological distress and suicidality (Hendricks et al. 2015). Further, Bouso et al. (2012) found that regular ayahuasca users scored lower on every psychopathology measure they administered compared to non-users who were similar in sex, age, education, and income. When evaluating the abuse potential of psilocybin according to the 8 factors of the U.S. Controlled Substances Act, Johnson et al. (2018) concluded that there is limited harm associated with the drug. Lastly, rather than being a gateway drug, psychedelic users are at a 40% reduced risk of abusing opiates in the last year (Pisano et al. 2017), and they have not been shown to induce dependence (Rucker et al. 2016). Given the rapidly rising rates of opiate abuse in older adults (SAMHSA 2017), this could be another potential benefit for this population. This is not to say that psychedelics are risk-free; they can induce experiences that are incredibly psychologically challenging, particularly when used in the absence of proper "set" and "setting" (Barret et al. 2016). However, limited harm has been reported in the new era of psychedelic research, which utilizes rigorous preparation, support, and integration procedures. Indeed, Ross et al. (2016) noted that in the new era of psychedelic research, over 2000 participants have been run through carefully monitored sessions with zero long-term aversive side effects reported (see Johnson et al. 2008 for safety guidelines).

Future Directions

There are several logistical and practical concerns that must be addressed to implement psychedelic treatment for age-related changes in cognition and affect. First, researchers need to identify when the best time is for individuals to take these substances to maximize their therapeutic properties. Perhaps taking them in early adulthood can buffer against downstream effects from chronic traits that psychedelics have been shown to change (i.e., creativity, executive functioning, openness to experience, depression, pessimism). On the other hand, it is still unclear how long psychedelic-related changes in cognitive/affective processing are maintained. While several contemporary studies have demonstrated changes lasting for at least a year (Gasser et al. 2014, 2015; Griffiths et al. 2008, 2011) and there is evidence that some changes endure as long as 25 years after a single session (Doblin 1991), other studies suggest that "booster" sessions may be valuable (Barbosa et al. 2009; Noorani et al. 2018). It seems likely that more robust longitudinal studies will emerge as the number of experimental studies has skyrocketed in recent years, and these can inform researchers about optimal timing, dosage, and number of sessions required.

The extent to which all of these changes generalize to older adults is another remaining question. Given the unique changes and life challenges associated with older adulthood, the treatments designed for younger individuals would not be expected to always be appropriate for older adults (and vice versa). For example, treatments like cognitive behavioral therapy (CBT) for mental illness are equally effective in younger and older adults but administered differently (Laidlaw 2014). Older adult CBT focuses on additional concerns such as mobility, bereavement, loneliness, and medical issues that are not common concerns for younger adults. In the same way, psychedelic treatment for young adults may differ in its implementation compared to older adults, and this warrants future study. In any case, some contemporary psychedelic studies have incorporated older adults and demonstrated a variety of positive outcomes (Griffiths et al. 2016; Ross et al. 2016); thus, there is emerging evidence that administering psychedelics during late-life can lead to cognitive and affective changes.

Conclusion

In short, the reviewed literature demonstrates robust theoretical links between psychedelics and changes in cognition and affect associated with older age. Though many older adults suffer declines in creativity and executive functions, psychedelics have been shown to boost creativity and have been related to improved executive functioning. Older adulthood has also been associated with reduced openness to experience, empathy, and meaningful experiences, all of which can be increased by psychedelic drugs. Their compelling therapeutic potential for depression, pessimism, suicide, and palliative care may also be of benefit to the elderly. Enhanced neurogenesis, neuroplasticity, connectedness, and mystical experiences have been argued to underlie many of the cognitive and affective changes. Finally, recent studies endorse that these drugs are relatively safe when used with professional preparation and supervision. Given that several of these studies have utilized older adults, it seems that they can be implemented into this population. Altogether, the prior research supports that using psychedelics to treat age-related changes in cognition and affect can be a viable, and likely impactful, area of study. This review proposes a novel area of research, and the findings from our critical analysis of the background literature reveal that researchers should consider self-selection biases, experimenter biases, standardized dosages, control groups, and generalizability to improve future experimental methodology in psychedelic science.

Compliance with Ethical Standards

Conflict of Interest The authors declare that they have no conflict of interest.

References

  1. Aday, J. S., Bloesch, E. K., & Davoli, C. C. (2019). Beyond LSD: A broader psychedelic zeitgeist during the early to mid-20th century. Journal of Psychoactive Drugs, 51, 210-217. https://doi.org/10.1080/02791072.2019.158196.
  2. Barbosa, P. C. R., Cazorla, I. M., Giglio, J. S., & Strassman, R. (2009). A six-month prospective evaluation of personality traits, psychiatric symptoms and quality of life in ayahuasca-naïve subjects. Journal of Psychoactive Drugs, 41, 205-212.
  3. Barret, F. S., Bradstreet, M. P., Leoutsakos, J. M. S., Johnson, M. W., & Griffiths, R. R. (2016). The challenging experience questionnaire: Characterization of challenging experiences with psilocybin mushrooms. Journal of Psychopharmacology, 30, 1279-1295. https://doi.org/10.1177/0269881116678781.
  4. Barrett, F. S., & Griffiths, R. R. (2017). Classic hallucinogens and mystical experiences: Phenomenology and neural correlates. In A. L. Halberstadt, F. X. Vollenweider, & D. E. Nutt (Eds.), Behavioral neurobiology of psychedelic drugs (pp. 393-430). Springer: Berlin.
  5. Baudouin, A., Isingrini, M., & Vanneste, S. (2019). Executive functioning and processing speed in age-related differences in time estimation: A comparison of young, old, and very old adults. Aging, Neuropsychology, and Cognition, 26, 264-281. https://doi.org/10. 1080/13825585.2018.1426715.
  6. Bauer, B. (2019). Psilocybin receives FDA breakthrough treatment designation. Psychedelic Science Review. Retrieved from https://psychedelicreview.com/psilocybin-receives-fda-breakthroughtreatment-designation/.
  7. Baum, S. K. (1988). Meaningful life experiences for elderly persons. Psychological Reports, 63, 427-433. https://doi.org/10.2466/pr0.1988.63.2.427.
  8. Blazer, D. G. (2003). Depression in late life: Review and commentary. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 58, M249-M265. https://doi.org/10.1093/gerona/58.3.M249.
  9. Bouso, J. C., González, D., Fondevila, S., Cutchet, M., Fernández, X., Barbosa, P. C. R., et al. (2012). Personality, psychopathology, life attitudes and neuropsychological performance among ritual users of ayahuasca: A longitudinal study. PLoS One, 7, 1-13. https://doi.org/10.1371/journal.pone.0042421.
  10. Bouso, J. C., Palhano-Fontes, F., Rodríguez-Fornells, A., Ribeiro, S., Sanches, R., Crippa, J. A. S. ... & Riba, J. (2015). Long-term use of psychedelic drugs is associated with differences in brain structure and personality in humans. European Neuropsychopharmacology, 25, 483-492. https://doi.org/10.1016/j.euroneuro.2015.01.008.
  11. Bouso, J. C., dos Santos, R. G., Alcázar-Córcoles, M. Á., & Hallak, J. E. (2018). Serotonergic psychedelics and personality: A systematic review of contemporary research. Neuroscience & Biobehavioral Reviews, 87, 118-132. https://doi.org/10.1016/j.neubiorev.2018.02. 004.
  12. Breitbart, W., Rosenfeld, B., Pessin, H., Applebaum, A., Kulikowski, J., & Lichtenthal, W. G. (2015). Meaning-centered group psychotherapy: An effective intervention for improving psychological well-being in patients with advanced cancer. Journal of Clinical Oncology, 33, 749-754.
  13. Brodwin, E. (2018). Evidence is mounting that psychedelic drugs can help treat diseases. Here are the most promising uses. Business Insider. Retrieved from https://www.businessinsider.com/most-promising-uses-psychedelic-drugs-medicine-science-2018-10.
  14. Camacho, T. C., Strawbridge, W. J., Cohen, R. D., & Kaplan, G. A. (1993). Functional ability in the oldest old: Cumulative impact of risk factors from the preceding two decades. Journal of Aging and Health, 5, 439-454.
  15. Carhart-Harris, R. L. (2018). The entropic brain - Revisited. Neuropharmacology, 142, 167-178. https://doi.org/10.1016/j. neuropharm.2018.03.010.
  16. Carhart-Harris, R. L. (2019). How do psychedelics work? Current Opinion in Psychiatry, 32, 16-21. https://doi.org/10.1097/YCO. 0000000000000467.
  17. Carhart-Harris, R. L., Erritzoe, D., Williams, T., Stone, J.M., Reed, L. J., Colasanti, A. ... & Hobden, P. (2012). Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin. Proceedings of the National Academy of Sciences, 109, 2138-2143. https://doi.org/10.1073/pnas.1119598109
  18. Carhart-Harris, R. L., Kaelen, M., & Nutt, D. (2014). How do hallucinogens work on the brain? The Psychologist, 27, 662-665.
  19. Carhart-Harris, R. L., Bolstridge, M., Rucker, J., Day, C. M., Erritzoe, D., Kaelen, M. & ... Taylor, D. (2016). Psilocybin with psychological support for treatment-resistant depression: An open-label feasibility study. The Lancet Psychiatry, 3, 619-627. https://doi.org/10.1016/S2215-0366(16)30065-7.
  20. Carhart-Harris, R. L., Erritzoe, D., Haijen, E., Kaelen, M., & Watts, R. (2018). Psychedelics and connectedness. Psychopharmacology, 235, 547-550. https://doi.org/10.1007/s00213-017-4701-y.
  21. Carroll, A. E. (2017). Can psychedelics be therapy? Allow research to find out. New York Times. Retrieved from https://www.nytimes.com/2017/07/17/upshot/can-psychedelics-be-therapy-allow-research-to-find-out.html.
  22. Catlow, B. J., Song, S., Paredes, D. A., Kirstein, C. L., & Sanchez-Ramos, J. (2013). Effects of psilocybin on hippocampal neurogenesis and extinction of trace fear conditioning. Experimental Brain Research, 228, 481-491. https://doi.org/10.1007/s00221-013-3579-0.
  23. Catlow, B. J., Jalloh, A., & Sanchez-Ramos, J. (2016). Hippocampal neurogenesis: Effects of psychedelic drugs. In V. Preedy (Ed.), Neuropathology of drug addictions and substance misuse (pp. 821-831). London: Academic.
  24. Cesari, M., Vellas, B., & Gambassi, G. (2013). The stress of aging. Experimental Gerontology, 48, 451-456.
  25. Chang, E. C., Elizabeth, A. Y., Lee, J. Y., Hirsch, J. K., Kupfermann, Y., & Kahle, E. R. (2013). An examination of optimism/pessimism and suicide risk in primary care patients: Does belief in a changeable future make a difference? Cognitive Therapy and Research, 37, 796-804. https://doi.org/10.1007/s10608-012-9505-0.
  26. Charles, S. T., & Carstensen, L. L. (2010). Social and emotional aging. Annual Review of Psychology, 61, 383-409.
  27. Christoffel, D. J., Golden, S. A., & Russo, S. J. (2011). Structural and synaptic plasticity in stress-related disorders. Reviews in the Neurosciences, 22, 535-549. https://doi.org/10.1515/RNS.2011.044.
  28. Cohen, S. (1965). LSD and the anguish of dying. Harper's Magazine, 231, 69-72.
  29. De Leo, D., & Meneghel, G. (2001). The elderly and suicide. In D. Wassermann (Ed.), Suicide: An unnecessary death (pp. 195-207). London: Martin Dunitz.
  30. Doblin, R. (1991). Pahnke's "Good Friday experiment": A long-term follow-up and methodological critique. Journal of Transpersonal Psychology, 23, 1-28
  31. Donnellan, M. B., & Lucas, R. E. (2008). Age differences in the Big Five across the life span: Evidence from two national samples. Psychology and Aging, 23, 558-566. https://doi.org/10.1037/a0012897
  32. Erritzoe, D., Roseman, L., Nour, M. M., MacLean, K., Kaelen, M., Nutt, D. J., & Carhart-Harris, R. L. (2018). Effects of psilocybin therapy on personality structure. Acta Psychiatrica Scandinavica, 138, 368-378. https://doi.org/10.1111/acps.12904.
  33. Fisher, G. (1970). Psychotherapy for the dying: Principles and illustrative cases with special reference to the use of LSD. OMEGA-Journal of Death and Dying, 1, 3-15.
  34. Frecska, E., Móré, C. E., Vargha, A., & Luna, L. E. (2012). Enhancement of creative expression and entoptic phenomena as after-effects of repeated ayahuasca ceremonies. Journal of Psychoactive Drugs, 44, 191-199. https://doi.org/10.1080/02791072.2012.703099.
  35. Galvan, V., & Jin, K. (2007). Neurogenesis in the aging brain. Clinical Interventions in Aging, 2, 605-610.
  36. Garcia-Romeu, A., Griffiths, R. R., & Johnson, M. W. (2014). Psilocybin-occasioned mystical experiences in the treatment of tobacco addiction. Current Drug Abuse Reviews, 7, 157-164. https://doi.org/10.2174/1874473708666150107121331.
  37. Garcia-Romeu, A., Davis, A. K., Erowid, F., Erowid, E., Griffiths, R. R., & Johnson, M. W. (2019). Cessation and reduction in alcohol consumption and misuse after psychedelic use. Journal of Psychopharmacology. https://doi.org/10.1177/0269881119845793.
  38. Gasser, P., Holstein, D., Michel, Y., Doblin, R., Yazar-Klosinski, B., Passie, T., & Brenneisen, R. (2014). Safety and efficacy of lysergic acid diethylamide-assisted psychotherapy for anxiety associated with life-threatening diseases. The Journal of Nervous and Mental Disease, 202, 513-520.
  39. Gasser, P., Kirchner, K., & Passie, T. (2015). LSD-assisted psychotherapy for anxiety associated with a life-threatening disease: A qualitative study of acute and sustained subjective effects. Journal of Psychopharmacology, 29, 57-68.
  40. Goh, J. O., & Park, D. C. (2009). Neuroplasticity and cognitive aging: The scaffolding theory of aging and cognition. Restorative Neurology and Neuroscience, 27, 391-403
  41. Goodden, J. (2017). Riding so high: The Beatles and drugs. Fairfield: Pepper & Pearl.
  42. Gregory, T., Nettelbeck, T., & Wilson, C. (2010). Openness to experience, intelligence, and successful ageing. Personality and Individual Differences, 48, 895-899.
  43. Griffiths, R. R., Richards, W. A., McCann, U., & Jesse, R. (2006). Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance. Psychopharmacology, 187, 268-283. https://doi.org/10.1007/s00213-006-0457-5.
  44. Griffiths, R., Richards, W., Johnson, M., McCann, U., & Jesse, R. (2008). Mystical-type experiences occasioned by psilocybin mediate the attribution of personal meaning and spiritual significance 14 months later. Journal of Psychopharmacology, 22, 621-632. https://doi.org/10.1177/0269881108094300.
  45. Griffiths, R. R., Johnson, M. W., Richards, W. A., Richards, B. D., McCann, U., & Jesse, R. (2011). Psilocybin occasioned mystical-type experiences: Immediate and persisting dose-related effects. Psychopharmacology, 218, 649-665. https://doi.org/10.1007/s00213-011-2358-5.
  46. Griffiths, R. R., Johnson, M. W., Carducci, M. A., Umbricht, A., Richards, W. A., Richards, B. D. ... & Klinedinst, M. A. (2016). Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial. Journal of Psychopharmacology, 30, 1181-1197. https://doi.org/10.1177/0269881116675513.
  47. Grob, C. S., Danforth, A. L., Chopra, G. S., Hagerty, M., McKay, C. R., Halberstadt, A. L., & Greer, G. R. (2011). Pilot study of psilocybin treatment for anxiety in patients with advanced-stage cancer. Archives of General Psychiatry, 68, 71-78. https://doi.org/10. 1001/archgenpsychiatry.2010.116.
  48. Grob, C. S., Bossis, A. P., & Griffiths, R. R. (2013). Use of the classic hallucinogen psilocybin for treatment of existential distress associated with cancer. In B. I. Carr & J. Steele (Eds.), Psychological aspects of Cancer (pp. 291-308). Boston: Springer.
  49. Grof, S., Goodman, L. E., Richards, W. A., & Kurland, A. A. (1973). LSD-assisted psychotherapy in patients with terminal cancer. International Pharmacopsychiatry, 8, 129-144.
  50. Grühn, D., Rebucal, K., Diehl, M., Lumley, M., & Labouvie-Vief, G. (2008). Empathy across the adult lifespan: Longitudinal and experience-sampling findings. Emotion, 8, 753-765. https://doi.org/10.1037/a0014123.
  51. Harman, W. W., McKim, R. H., Mogar, R. E., Fadiman, J., & Stolaroff, M. J. (1966). Psychedelic agents in creative problem-solving: A pilot study. Psychological Reports, 19, 211-227.
  52. Heisel, M. J., & Flett, G. L. (2008). Psychological resilience to suicide ideation among older adults. Clinical Gerontologist, 31, 51-70.
  53. Hendricks, P. S., Thorne, C. B., Clark, C. B., Coombs, D. W., & Johnson, M. W. (2015). Classic psychedelic use is associated with reduced psychological distress and suicidality in the United States adult population. Journal of Psychopharmacology, 29, 280-288. https://doi.org/10.1177/0269881114565653.
  54. Hendy, K. (2018). Placebo problems: Boundary work in the psychedelic science renaissance. In B. C. Labate & C. Cavnar (Eds.), Plant medicines, healing and psychedelic science: Cultural perspectives (pp. 151-166). Cham: Springer. https://doi.org/10.1007/978-3-319-76720-8_9.
  55. Honig, E. (2019). A growing push to loosen laws around psilocybin, treat mushrooms as medicine. In NPR Retrieved from https://www.npr.org/sections/health-shots/2019/05/07/720828367/a-growing-push-to-loosen-laws-around-psilocybin-treat-mushrooms-as-medicine.
  56. Jacobs, B. L., Van Praag, H., & Gage, F. H. (2000). Adult brain neurogenesis and psychiatry: A novel theory of depression. Molecular Psychiatry, 5, 262-269.
  57. Johansen, P. O., & Krebs, T. S. (2015). Psychedelics not linked to mental health problems or suicidal behavior: A population study. Journal of Psychopharmacology, 29, 270-279. https://doi.org/10.1177/0269881114568039.
  58. Johnson, M. W., Richards, W. A., & Griffiths, R. R. (2008). Human hallucinogen research: Guidelines for safety. Journal of Psychopharmacology, 22, 603-620. https://doi.org/10.1177/0269881108093587.
  59. Johnson, M. W., Griffiths, R. R., Hendricks, P. S., & Henningfield, J. E. (2018). The abuse potential of medical psilocybin according to the 8 factors of the Controlled Substances Act. Neuropharmacology, 142, 143-166. https://doi.org/10.1016/j.neuropharm.2018.05.012.
  60. Jungaberle, H., Thal, S., Zeuch, A., Rougemont-Bücking, A., von Heyden, M., Aicher, H., & Scheidegger, M. (2018). Positive psychology in the investigation of psychedelics and entactogens: A critical review. Neuropharmacology, 142, 179-199. https://doi.org/10.1016/j.neuropharm.2018.06.034.
  61. Kelmendi, B., Corlett, P., Ranganathan, M., D'Souza, C., & Krystal, J. H. (2016). The role of psychedelics in palliative care reconsidered: A case for psilocybin. Journal of Psychopharmacology, 30, 1212-1214. https://doi.org/10.1177/0269881116675781.
  62. Kumar, P. S., Anish, P. K., & George, B. (2015). Risk factors for suicide in elderly in comparison to younger age groups. Indian Journal of Psychiatry, 57, 249. https://doi.org/10.4103/0019-5545.166614.
  63. Kuypers, K. P. C., Riba, J., de la Fuente Revenga, M., Barker, S., Theunissen, E. L., & Ramaekers, J. G. (2016). Ayahuasca enhances creative divergent thinking while decreasing conventional convergent thinking. Psychopharmacology, 233, 3395-3403. https://doi.org/10.1007/s00213-016-4377-8.
  64. Laidlaw, K. (2014). CBT for older people: An introduction. Dorchester: Sage.
  65. Lebedev, A. V., Lövdén, M., Rosenthal, G., Feilding, A., Nutt, D. J., & Carhart-Harris, R. L. (2015). Finding the self by losing the self: Neural correlates of ego-dissolution under psilocybin. Human Brain Mapping, 36, 3137-3153. https://doi.org/10.1002/hbm.22833.
  66. Lebedev, A. V., Kaelen, M., Lövdén, M., Nilsson, J., Feilding, A., Nutt, D. J., & Carhart-Harris, R. L. (2016). LSD-induced entropic brain activity predicts subsequent personality change. Human Brain Mapping, 37, 3203-3213. https://doi.org/10.1002/hbm.23234.
  67. Lima da Cruz, R. V., Moulin, T. C., Petiz, L. L., & Leao, R. N. (2018). A single dose of 5-MeO-DMT stimulates cell proliferation, neuronal survivability, morphological and functional changes in adult mice ventral dentate gyrus. Frontiers in Molecular Neuroscience, 11, 1-11.
  68. Ly, C., Greb, A. C., Cameron, L. P., Wong, J. M., Barragan, E. V., Wilson, P. C., & ... Duim, W. C. (2018). Psychedelics promote structural and functional neural plasticity. Cell Reports, 23, 3170-3182. https://doi.org/10.1016/j.celrep.2018.05.022.
  69. Lyons, T., & Carhart-Harris, R. L. (2018). More realistic forecasting of future life events after psilocybin for treatment-resistant depression. Frontiers in Psychology, 9, 1-11. https://doi.org/10.3389/fpsyg.2018.01721.
  70. MacLean, K. A., Johnson, M. W., & Griffiths, R. R. (2011). Mystical experiences occasioned by the hallucinogen psilocybin lead to increases in the personality domain of openness. Journal of Psychopharmacology, 25, 1453-1461. https://doi.org/10.1177/0269881111420188.
  71. McGlothlin, W., Cohen, S., & McGlothlin, M. S. (1967). Long lasting effects of LSD on normals. Archives of General Psychiatry, 17, 521-532.
  72. Millière, R., Carhart-Harris, R. L., Roseman, L., Trautwein, F. M., & Berkovich-Ohana, A. (2018). Psychedelics, meditation, and self-consciousness. Frontiers in Psychology, 9, 1-29. https://doi.org/10.3389/fpsyg.2018.01475.
  73. Mok, R. M., Myers, N. E., Wallis, G., & Nobre, A. C. (2016). Behavioral and neural markers of flexible attention over working memory in aging. Cerebral Cortex, 26, 1831-1842. https://doi.org/10.1093/cercor/bhw011.
  74. Morales-García, J. A., de la Fuente Revenga, M., Alonso-Gil, S., Rodríguez-Franco, M. I., Feilding, A., Perez-Castillo, A., & Riba, J. (2017). The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro. Scientific Reports, 7, 1-13. https://doi.org/10.1038/s41598-017-05407-9.
  75. Mossello, E., Boncinelli, M., Caleri, V., Cavallini, M. C., Palermo, E., Di Bari, M., ... & Masotti, G. (2008). Is antidepressant treatment associated with reduced cognitive decline in Alzheimer's disease? Dementia and Geriatric Cognitive Disorders, 25, 372-379.
  76. Nichols, D. E. (2016). Psychedelics. Pharmacological Reviews, 68, 264-355. https://doi.org/10.1124/pr.115.011478.
  77. Noorani, T., Garcia-Romeu, A., Swift, T. C., Griffiths, R. R., & Johnson, M. W. (2018). Psychedelic therapy for smoking cessation: Qualitative analysis of participant accounts. Journal of Psychopharmacology, 32, 756-769.
  78. Palhano-Fontes, F., Andrade, K. C., Tofoli, L. F., Santos, A. C., Crippa, J. A. S., Hallak, J. E. ... & de Araujo, D. B. (2015). The psychedelic state induced by ayahuasca modulates the activity and connectivity of the default mode network. PLoS One, 10, 1-13. https://doi.org/10.1371/journal.pone.0118143.
  79. Pisano, V. D., Putnam, N. P., Kramer, H. M., Franciotti, K. J., Halpern, J. H., & Holden, S. C. (2017). The association of psychedelic use and opioid use disorders among illicit users in the United States. Journal of Psychopharmacology, 31, 606-613. https://doi.org/10.1177/0269881117691453.
  80. Pokorny, T., Preller, K. H., Kometer, M., Dziobek, I., & Vollenweider, F. X. (2017). Effect of psilocybin on empathy and moral decision-making. International Journal of Neuropsychopharmacology, 20, 747-757. https://doi.org/10.1093/ijnp/pyx047.
  81. Pollan, M. (2018). The new science of psychedelics. Wall Street Journal. Retrieved from https://www.wsj.com/articles/the-new-science-of-psychedelics-1525360091.
  82. Preller, K. H., Herdener, M., Pokorny, T., Planzer, A., Kraehenmann, R., Stämpfli, P. ... & Vollenweider, F. X. (2017). The fabric of meaning and subjective effects in LSD-induced states depend on serotonin 2A receptor activation. Current Biology, 27, 451-457. https://doi.org/10.1016/j.cub.2016.12.030.
  83. Price, K. A., & Tinker, A. M. (2014). Creativity in later life. Maturitas, 78, 281-286. https://doi.org/10.1016/j.maturitas.2014.05.025.
  84. Prochazkova, L., Lippelt, D. P., Colzato, L. S., Kuchar, M., Sjoerds, Z., & Hommel, B. (2018). Exploring the effect of microdosing psychedelics on creativity in an open-label natural setting. Psychopharmacology, 235, 3401-3413. https://doi.org/10.1007/s00213-018-5049-7.
  85. Roseman, L., Nutt, D. J., & Carhart-Harris, R. L. (2018). Quality of acute psychedelic experience predicts therapeutic efficacy of psilocybin for treatment-resistant depression. Frontiers in Pharmacology, 8, 1-10. https://doi.org/10.3389/fphar.2017.00974.
  86. Ross, S., Bossis, A., Guss, J., Agin-Liebes, G., Malone, T., Cohen, B. ... & Su, Z. (2016). Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: A randomized controlled trial. Journal of Psychopharmacology, 30, 1165-1180. https://doi.org/10.1177/0269881116675512.
  87. Rucker, J. J. H., Jelen, L. A., Flynn, S., Frowde, K. D., & Young, A. H. (2016). Psychedelics in the treatment of unipolar mood disorders: A systematic review. Journal of Psychopharmacology, 30, 1220-1229. https://doi.org/10.1177/0269881116679368
  88. Russ, S. L., Carhart-Harris, R. L., Maruyama, G., & Elliott, M. S. (2019). Replication and extension of a model predicting response to psilocybin. Psychopharmacology. https://doi.org/10.1007/s00213-019-05279-z.
  89. Salthouse, T. A. (2009). When does age-related cognitive decline begin? Neurobiology of Aging, 30, 507-514.
  90. SAMHSA (2017) Opioid misuse increases among older adults. Retrieved from https://www.samhsa.gov/data/sites/default/files/report_3186/Spotlight-3186.html.
  91. Scheibe, S., & Carstensen, L. L. (2010). Emotional aging: Recent findings and future trends. The Journals of Gerontology: Series B, 65, 135-144.
  92. Schmid, Y., & Liechti, M. E. (2018). Long-lasting subjective effects of LSD in normal subjects. Psychopharmacology, 235, 535-545. https://doi.org/10.1007/s00213-017-4733-3.
  93. Selemon, L. D. (2013). A role for synaptic plasticity in the adolescent development of executive function. Translational Psychiatry, 3, 1- 9. https://doi.org/10.1038/tp.2013.7.
  94. Sessa, B. (2008). Is it time to revisit the role of psychedelic drugs in enhancing human creativity? Journal of Psychopharmacology, 22, 821-827. https://doi.org/10.1177/0269881108091597.
  95. Sheline, Y. I., Barch, D. M., Price, J. L., Rundle, M. M., Vaishnavi, S. N., Snyder, A. Z., ... & Raichle, M. E. (2009). The default mode network and self-referential processes in depression. Proceedings of the National Academy of Sciences, 106, 1942-1947. https://doi.org/10.1073/pnas.0812686106.
  96. Shelton, R. C., & Hendricks, P. S. (2016). Psilocybin and palliative end-of-life care. Journal of Psychopharmacology, 30, 1207-1208. https://doi.org/10.1177/0269881116675764.
  97. Silvia, P. J., Nusbaum, E. C., Berg, C., Martin, C., & O'Connor, A. (2009). Openness to experience, plasticity, and creativity: Exploring lower-order, high-order, and interactive effects. Journal of Research in Personality, 43, 1087-1090. https://doi.org/10.1016/j.jrp.2009.04.015.
  98. Smigielski, L., Scheidegger, M., Kometer, M., & Vollenweider, F. X. (2019). Psilocybin-assisted mindfulness training modulates self-consciousness and brain default mode network connectivity with lasting effects. NeuroImage, 196, 207-215. https://doi.org/10.1016/j.neuroimage.2019.04.009.
  99. Smith, G. E. (2016). Healthy cognitive aging and dementia prevention. American Psychologist, 71, 268-275.
  100. Suri, G., & Gross, J. J. (2012). Emotion regulation and successful aging. Trends in Cognitive Sciences, 16, 409-410.
  101. Swanson, L. R. (2018). Unifying theories of psychedelic drug effects. Frontiers in Pharmacology, 9, 1-23. https://doi.org/10.3389/fphar.2018.00172.
  102. Thiessen, M. S., Walsh, Z., Bird, B. M., & Lafrance, A. (2018). Psychedelic use and intimate partner violence: The role of emotion regulation. Journal of Psychopharmacology, 32, 749-755.
  103. Uthaug, M. V., van Oorsouw, K., Kuypers, K. P. C., van Boxtel, M., Broers, N. J., Mason, N. L. ... & Ramaekers, J. G. (2018). Subacute and long-term effects of ayahuasca on affect and cognitive thinking style and their association with ego dissolution. Psychopharmacology, 235, 2979-2989. https://doi.org/10.1007/s00213-018-4988-3.
  104. Vollenweider, F. X., & Kometer, M. (2010). The neurobiology of psychedelic drugs: Implications for the treatment of mood disorders. Nature Reviews Neuroscience, 11, 642-651. https://doi.org/10.1038/nrn2884
  105. Vollenweider, F. X., Vollenweider-Scherpenhuyzen, M. F., Bäbler, A., Vogel, H., & Hell, D. (1998). Psilocybin induces schizophrenia-like psychosis in humans via a serotonin-2 agonist action. Neuroreport, 9, 3897-3902.
  106. Wang, S., & Blazer, D. G. (2015). Depression and cognition in the elderly. Annual Review of Clinical Psychology, 11, 331-360. https://doi.org/10.1146/annurev-clinpsy-032814-112828.
  107. Xu, W., Yu, J. T., Tan, M. S., & Tan, L. (2015). Cognitive reserve and Alzheimer's disease. Molecular Neurobiology, 51, 187-208. https://doi.org/10.1007/s12035-014-8720-y.
  108. Zegans, L. S., Pollard, J. C., & Brown, D. (1967). The effects of LSD-25 on creativity and tolerance to regression. Archives of General Psychiatry, 16, 740-749.
  109. Zeki Al Hazzouri, A., Vittinghoff, E., Byers, A., Covinsky, K., Blazer, D., Diem, S., ... Yaffe, K. (2014). Long-term cumulative depressive symptom burden and risk of cognitive decline and dementia among very old women. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 69, 595-601. https://doi.org/10.1093/gerona/glt139.
  110. Zhang, G., & Stackman, R. W., Jr. (2015). The role of serotonin 5-HT2A receptors in memory and cognition. Frontiers in Pharmacology, 6, 1-17. https://doi.org/10.3389/fphar.2015.00225.



search on psilosophy:  
 

TutorialS ]   [ ForuM ]   [ SpecieS ]   [ GalerY (pl) ]   [ TripograM ]   [ PsilosOpediuM ]  

© psilosophy 2001-2021