Psychedelics and mental health: a population study

This survey study that included psychedelics users (n=21.967, 13% of total) found no associations between psychedelics use and mental health outcomes. It even found a slightly lower rate of mental health problems for those who used psychedelics.


“Background The classical serotonergic psychedelics LSD, psilocybin, mescaline are not known to cause brain damage and are regarded as non-addictive. Clinical studies do not suggest that psychedelics cause long-term mental health problems. Psychedelics have been used in the Americas for thousands of years. Over 30 million people currently living in the US have used LSD, psilocybin, or mescaline.

Objective To evaluate the association between the lifetime use of psychedelics and current mental health in the adult population.

Method Data drawn from years 2001 to 2004 of the National Survey on Drug Use and Health consisted of 130,152 respondents, randomly selected to be representative of the adult population in the United States. Standardized screening measures for past-year mental health included serious psychological distress (K6 scale), mental health treatment (inpatient, outpatient, medication, needed but did not receive), symptoms of eight psychiatric disorders (panic disorder, major depressive episode, mania, social phobia, general anxiety disorder, agoraphobia, posttraumatic stress disorder, and non-affective psychosis), and seven specific symptoms of non-affective psychosis. We calculated weighted odds ratios by multivariate logistic regression controlling for a range of sociodemographic variables, the use of illicit drugs, risk-taking behavior, and exposure to traumatic events.

Results 21,967 respondents (13.4% weighted) reported lifetime psychedelic use. There were no significant associations between lifetime use of any psychedelics, lifetime use of specific psychedelics (LSD, psilocybin, mescaline, peyote), or past year use of LSD and increased rate of any of the mental health outcomes. Rather, in several cases psychedelic use was associated with a lower rate of mental health problems. Conclusion We did not find the use of psychedelics to be an independent risk factor for mental health problems.

Authors: Teri S. Krebs & Pål-Ørjan Johansen


This study is followed up by another survey by Johansen & Krebs (2015) that found similar results.


Psychedelics and Mental Health: A Population Study

Psychedelics are not known to cause brain damage and are non-addictive. Over 30 million people have used them in the US.


Psychedelic plants have been used for thousands of years for celebratory, religious or healing purposes. They are not known to cause damage to the brain or other organs of the body, or cause withdrawal symptoms, elicit addiction or compulsive use, or cause birth defects or genetic damage.

Expert assessments suggest that psilocybin and other psychedelics cause less harm than alcohol, tobacco, and most other common recreational drugs. There are no well-documented case reports of long-term mental health problems following use of psychedelics.

Ethics Statement

This study was exempt from review by the Regional Committee for Medical Research Ethics because all data were public.

Source, Population and Data

The NSDUH survey provides estimates of substance use and mental health indicators from a randomly-selected sample representative of the general US civilian non-institutionalized adult population. It is conducted by trained interviewers in homes and uses headphones and computer-based data collection.

Use of Psychedelics

We examined participants’ lifetime psychedelic use, and examined use of each substance separately. Information was also available on past year use of LSD, but not psilocybin or mescaline.

Mental Health Indicators

Serious psychological distress is assessed using the K6 scale, which asks about frequency of six symptoms of psychological distress. A score of 13 or more on the K6 scale is the validated and recommended cut-point for serious psychological distress.

Past year mental health treatment included inpatient stays, outpatient stays, psychiatric medication prescription, and felt a need but did not receive mental health treatment.

Psychiatric symptom indicators were evaluated using the short form of the World Health Organization Composite International Diagnostic Interview (CIDI-SF), which consists of between three to eight questions per disorder. We also examined each of the seven symptoms of non-affective psychosis individually.

Control Variables

We selected control variables based on associations with mental health in previous research. These variables included age at interview, gender, race/ethnicity, education, household income, marital status, likes to test self with risky behavior, lifetime exposure to an extremely stressful event, and past year use of LSD.

Data Analysis

We calculated associations between past year mental health indicators and use of psychedelics using multivariate logistic regression, and also calculated associations in subgroups based on sex, age, past year illicit drug use, and lifetime exposure to an extremely stressful event.

The estimated associations between the use of psychedelics and mental health outcomes are presented as adjusted odds ratios, 95% confidence intervals, and p-values.

We used multivariate logistic regression with a standard alpha of 0.05, and had at least 10 events per predictor variable for all analyses, with 21 to 379 events per predictor variable for mental health indicators besides the specific psychotic symptoms.

Characteristics of Psychedelic Users

The sample consisted of 130,152 respondents, of which 21,979 (13.4% weighted) reported lifetime use of any psychedelic. Psychedelic users had higher rates of all indicators of mental health problems, even after adjusting for confounding factors.

Lifetime psilocybin use, lifetime mescaline use, and past year LSD use were associated with lower rates of serious psychological distress.

Lifetime psychedelic use was not significantly associated with any of the mental health treatment variables. However, lifetime LSD use was significantly associated with a lower rate of receiving or needing mental health treatment.

Psychedelic use was not significantly associated with any of the eight past year psychiatric symptom indicators, but was significantly associated with a lower rate of one of the seven psychotic symptoms.

In a series of multivariate logistic regression analyses, there was no significant association between lifetime psychedelic use and greater risk of any mental health outcomes. Psychedelic users had a lower rate of symptoms of psychosis, generalized anxiety disorder, needed mental health treatment, symptoms of agoraphobia, and posttraumatic stress disorder than non-users, and a lower rate of symptoms of psychosis and the psychotic symptoms felt force inserting thoughts and felt force steal thoughts.

Native americans reported a high rate of lifetime psychedelic use and a high rate of lifetime peyote use, but excluding Native Americans changed the adjusted odds ratios on average less than 2%.

Wt %, weighted percentage. doi:10.1371/journal.pone.0063972.t002

Participants with missing data had minimal effect on the results and statistical significance was not affected.

We found no association between lifetime use of psychedelics and undesirable past year mental health outcomes, including serious psychological distress, mental health treatment, or symptoms of panic disorder, major depressive episode, mania, social phobia, generalized anxiety disorder, agoraphobia, post-traumatic stress disorder, or non-affective psychosis.


This study had a retrospective, cross-sectional design, and did not examine active drug or short-term effects. It is possible that psychedelic use has a negative effect on mental health for some individuals or groups, perhaps counterbalanced at a population level by a positive effect on mental health in others.

Clinical Studies in Healthy Volunteers

This large population survey found no association between the use of psychedelics and mental health problems. Eight recent double-blind, placebo-controlled studies of psilocybin in healthy volunteers found no evidence of lasting adverse effects.

Cross-sectional and Case-control Studies

A case-control study of Native Americans found that people who regularly used peyote and ayahuasca in religious services had better mental health than those who did not use peyote and ayahuasca. In a population study, any lifetime use of cocaine and/or psychedelics was associated with prior lifetime history of two or more of 15 psychotic symptoms, but not one psychotic symptom. However, in a retrospective study, no association was found between any lifetime use of psychedelics and panic attacks or depression.

‘‘Flashbacks’’ and Perceptual Phenomena

In this study, lifetime use of psychedelics and past year use of LSD were not associated with past year symptoms of visual phenomena, panic attacks, psychosis, or overall serious psychological distress. Thus, the idea of ”flashbacks” or ”hallucinogen persisting perceptual disorder” is not supported.

A study on persistent visual symptoms found that only 5% of participants had ever used LSD, and there did not seem to be any relationship between drug use and visual symptoms. However, several people with persistent visual symptoms were later found to have other conditions.

A young man was diagnosed with HPPD and told that his vision was fine and somatization disorder was implied. He improved after psychotherapy for his depression and worries.

Comments on Case Reports

Several issues should be kept in mind when considering case reports of long-term psychiatric problems attributed to psychedelics, including that most adverse effects of psychedelics are short-lived, that mental illness and psychedelic use are prevalent in the population, and that many case reports do not rule-out preexisting psychiatric difficulties, life stresses, or use of other drugs. Some people attribute psychiatric symptoms to the use of psychedelics, but some health professionals may have a biased view. Caution should be used when generalizing from LSD to other psychedelics.

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