Epidemiology of classic psychedelic substances: results from a Norwegian internet convenience sample

Classic psychedelic substances such as psilocybin and LSD have seen renewed research interest because recent clinical trials suggest therapeutic potential for conditions including anxiety, depression, and substance use disorders. These substances—also including mescaline and DMT—primarily act via the serotonin 5-HT2A receptor and, while physiologically low in toxicity, can provoke psychologically challenging acute reactions and, more rarely, longer-lasting conditions such as hallucinogen persisting perception disorder (HPPD). Large population studies outside the Nordic context have linked prior psychedelic use with lower rates of some mental-health problems, and internet surveys have been used to characterise both benefits and risks of recreational psychedelic use, but data from non‑English speaking countries remain limited. Kvam and colleagues set out to map the epidemiology of classic psychedelic substance use in Norway by surveying adults who reported a memorable psychedelic experience. The primary aims were to describe characteristics of that most memorable experience and its acute and persisting effects, and secondary aims included examining self‑reported changes in mental disorders and substance‑use disorders as well as the occurrence, duration and severity of persisting adverse reactions including proxy measures for HPPD.

The study used an anonymous, retrospective online survey hosted on Nettskjema.no and conducted between 9 May and 19 August 2022. Inclusion criteria required participants to be aged 18 or older, fluent in Norwegian, and to have had a memorable experience after taking a classic psychedelic substance (LSD, psilocybin, 2C‑B, ayahuasca, DMT, 5‑MeO‑DMT, mescaline, or others). Experiences with ketamine and MDMA were excluded. Recruitment was via the Norwegian Association for Psychedelic Science, Rusopplysningen.no and various Facebook groups; participation was voluntary, anonymous and uncompensated. Only survey completers were analysed. The questionnaire comprised 119 items covering demographics, lifetime and past‑year psychedelic use, detailed characteristics of the most memorable experience (substance, setting, dose category, preparation, intent, support, co‑administration, integration), self‑reported mental disorders and substance‑use disorders, acute and persisting effects (including flashbacks and craving), and whether participants sought professional help. Three standardised instruments were included: the Ego‑Dissolution Inventory (EDI), the Emotional Breakthrough Inventory (EBI) and the Challenging Experience Questionnaire (CEQ); all were translated and pilot tested in Norwegian. Ethical oversight was local (Internal ethics committee, Department of Psychology, University of Oslo) and the study stored data on a secure service; identifiable information was not collected. Analyses were descriptive (frequencies, means, standard deviations). The investigators also used t‑tests to examine differences in frequency of psychedelic use between participants with and without self‑reported mental or substance‑use disorders. Analyses were performed in IBM SPSS. The extracted text does not clearly report the detailed procedures for scoring or handling missing data, nor the full results of any inferential tests beyond descriptive figures.

Of 841 survey completers, 770 participants met eligibility and were included in analyses; 555 (72%) were male, 208 (27%) female and seven (1%) non‑binary. The sample was skewed toward younger adults, with 88% aged 45 or younger, 63% reporting some higher education, and 86.6% unmarried. Median survey completion time was 20 minutes 26 seconds; the mean was substantially higher due to a right‑skewed distribution. Lifetime and recent use varied: only 51 participants (6.6%) reported a single lifetime psychedelic experience, 49% used a psychedelic one to five times in the past year and 21% reported no use in the past year. Attitudes were strongly favourable toward therapeutic use: 74% strongly agreed and 21% agreed that psychedelics should be used therapeutically. Regarding the most memorable experience, psilocybin was most commonly reported (53%), followed by LSD (33%), DMT (4.7%) and ayahuasca (4.4%). Participants most often considered their dose moderate (54%) or high (38%), and most remembered the experience quite clearly (41.6%) or very clearly (50.6%). Common settings were at home (33%), someone else’s home (21.9%) or outdoors (25.2%); 17.3% were alone and 39.9% received guidance or support. Although 28.1% reported collaboration with a therapist/guide/trip‑sitter, only 3.1% indicated the setting was a therapist’s clinic; among those who did collaborate, 63.9% rated the collaboration as very constructive. Motivations were primarily recreational/curiosity (46.1%) or therapeutic (42.3%); spiritual/religious reasons accounted for 8.7%. Preparation and intention were common: 45.6% prepared to a large extent and 25.6% to a very large extent; 35.5% endorsed intention to a large extent and 17.1% to a very large extent. Integration work after the experience was reported to a large extent by 46.8% and to a very large extent by 16.0%. Co‑administration occurred in 37.5% of cases, most often cannabis (30.3%), followed by MDMA (4.7%) and alcohol (2.9%). Large majorities reported psychological insights during the experience: 95.1% gained increased understanding of past events, 94.2% uncovered associations between current and past interpersonal relationships, and 92.7% discovered new or forgotten coping strategies. Average scores were EDI ≈58/100 per item and EBI ≈56/100 per item; CEQ averaged about 2.0 per item on a 0–5 scale. On life‑rank comparisons (scale 1–8), roughly 24–31% rated the experience among the top five or single most personally meaningful, spiritual or insightful; 14% ranked it among the top five or single most psychologically challenging. Persistent positive changes attributed to the experience were commonly reported: wellbeing/life satisfaction 91%, life purpose 86%, life meaning 84%, social relationships 82%, attitudes about life 89%, attitudes about nature 80%, attitudes about death 60%, mood 77%, behaviour 73% and spirituality 66%. Self‑reported or clinician‑assessed diagnoses were prevalent. The most commonly endorsed were depression (49.6%), daily smoking (41.7%), social anxiety (34.4%), suicidality (28.8%) and other substance abuse/addiction (26.4%); mean number of diagnoses was 2.46 (SD 2.10). Only 19.2% reported no mental disorder or substance‑use disorder. Most participants with pre‑existing conditions reported subjective improvement after the memorable experience; for example, 89.7% reported benefit for PTSD, 89.2% for depression and 83.8% for suicidality. Smoking showed lower perceived benefit (41.3%). A small subset reported worsening of conditions following the experience, most commonly psychosis (7.7%), other abuse/addiction (4.5%) and OCD (4.4%). Persisting adverse reactions were reported by 23.1% of participants. Duration distributions across the total sample included adverse reactions lasting a few days (10.6%), a few weeks (4.5%), months (3.8%) and more than one year (4.2%). The most prevalent persisting symptoms among those reporting adverse reactions were sadness/dejection (3.5% of the total sample), anxiety/nervousness (2.6%), and headache (1.8%). Only 15 respondents (1.9%) sought professional help for adverse reactions. Functional impact was uncommon: 5.2% reported moderate impairment and 0.5% reported severe impairment. For flashbacks/relived sensory experiences (screening for HPPD‑like symptoms), 75.2% reported none; durations reported included a few days (14.3%), weeks (3.6%), months (4.0%) and more than one year (2.9%). Most flashbacks were tolerated well; 1.6% reported impaired functioning due to flashbacks. The extracted text does not provide detailed inferential statistics or the results of t‑tests referenced in the methods.

Kvam and colleagues interpret these findings as an initial characterisation of memorable psychedelic experiences in a Norwegian convenience sample and the first survey of its kind in Norway. The discussion emphasises that the surveyed group was demographically skewed—predominantly male, younger than 46 and with higher education—and that most reported experiences involved psilocybin or LSD. Motivations in this sample (therapeutic and recreational) differed from some prior naturalistic studies that reported stronger spiritual motives for substances such as mescaline or 5‑MeO‑DMT. The investigators note high rates of preparation and integration among respondents, and that over 90% reported experiential insight into life events, relationships and coping strategies; these factors are aligned with elements emphasised in contemporary psychedelic‑assisted therapy. Regarding clinical implications, most participants with self‑reported mental‑health or substance‑use problems attributed improvements to their psychedelic experience, which the authors situate alongside emerging clinical trial evidence for conditions such as depression and alcohol use disorder. However, they caution that a small but meaningful minority experienced persistent adverse reactions, including symptoms consistent with prolonged perceptual disturbances; HPPD‑like phenomena were described as relatively rare and usually mild but occasionally lasting weeks, months or longer. The discussion also highlights a high rate of self‑reported craving for repeated psychedelic use—potentially indicating abuse risk—while distinguishing this from classical addictive potential, which is considered low; only a small number reported difficulty cutting down use. The authors acknowledge multiple limitations that constrain interpretation: cross‑sectional and retrospective design preventing causal inference; recall and response biases; inability to disentangle effects of a single memorable experience from other lifetime psychedelic exposures; selection bias via internet recruitment and likely overrepresentation of pro‑psychedelic attitudes (74% strongly agreed psychedelics should be used therapeutically); a non‑representative sample with higher education than the general population; inclusion of 5‑MeO‑DMT (whose classification as a classic psychedelic is debated); unknown or variable doses across substances; and reliance on self‑report without clinical confirmation. They therefore recommend replication in controlled clinical trials and additional naturalistic observational research rather than treating these findings as definitive.

The anonymous internet survey adds to knowledge about benefits and harms of recreational psychedelic experiences in Norway. In this self‑selected sample, most memorable experiences involved psilocybin or LSD, were undertaken for recreational or therapeutic reasons, and were accompanied by preparation and integration. Mental‑health and substance‑use problems were common and most participants reported subjective improvements following their experience. Adverse reactions were generally tolerable and transient, but a small subset reported persistent adverse effects lasting more than one year.