Treatment with LSD and psilocybin at the department of psychiatry at Frederiksberg Hospital in Denmark from 1960 to 1973: an analysis of 324 cases
Pernille Kølbæk, Søren Dinesen Østergaard, Jens Larsen
Nordic Journal of Psychiatry July 10, 2025 DOI: 10.1080/08039488.2025.2529449 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Retrospective cohort study Peer reviewed |
|---|---|
| Sample size | 324 |
| Population | Patients treated with LSD and/or psilocybin at the Department of Psychiatry at Frederiksberg Hospital in Denmark from 1960 to 1973 |
| Interventions | LSD psilocybin |
| Topics | Psilocybin LSD |
| Keywords | Hallucinogen |
| Key findings | Applicants for reparatory compensation received higher LSD doses and more treatments than non-applicants, and had a higher incidence of flashbacks (18.2% vs. 5.2%), but treatment responses did not differ significantly between groups. |
Abstract
Background Recent studies have suggested that psychedelics such as lysergic acid diethylamide (LSD) and psilocybin might benefit patients with mental illness. This revival calls for revisiting the field’s past experiences with these agents. From 1960 to 1973, many patients were treated with LSD and/or psilocybin at the Department of Psychiatry at Frederiksberg Hospital in Denmark. Here, we analyze the case material/medical records of 324 of these patients. Specifically, we aimed to estimate whether patients who applied for reparatory compensation (applicants; n = 93) as per the Danish LSD Damages Law had worse responses and were more affected by adverse events related to psychedelic treatment than those who did not (non-applicants; n = 231).Materials and Methods Data from the LSD archive at Frederiksberg City Archives were reviewed, and data regarding patient characteristics and LSD/psilocybin treatment (dose, effect, and adverse events) were extracted. Data were compared between applicants and non-applicants using independent samples t-tests, Mann–Whitney U tests, chi-square tests, and Fisher’s exact tests, as appropriate.Results Applicants were treated with higher LSD doses (median LSD dose-index: 31 vs. 21, p = 0.040) and received more treatments (median: 14 vs. 10, p = 0.005) than the non-applicants. Treatment responses did not differ significantly between applicants and non-applicants. Flashbacks were registered for a larger fraction of the applicants compared to non-applicants (18.2% vs. 5.2%, p < 0.001).Conclusions The high incidence of flashbacks should be taken into account in future clinical studies examining psychedelic treatment of patients with mental disorders.
Comparable studies
Other observational and cohort studies on LSD, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Increased Global Functional Connectivity Correlates with LSD-Induced Ego Dissolution. Human participants | 2016 | Observational cohort | |
| Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin Humans | 2017 | Observational study | |
| Classic psychedelic use is associated with reduced psychological distress and suicidality in the United States adult population. USA adult respondents from the National Survey on Drug Use and Health (2008-2012) | 2015 | Observational cohort | n = 190,000 |
| Psychedelics not linked to mental health problems or suicidal behavior: A population study Randomly selected United States adults | 2015 | Observational cohort | n = 135,095 |
| Whole-Brain Multimodal Neuroimaging Model Using Serotonin Receptor Maps Explains Non-linear Functional Effects of LSD. Healthy human participants | 2018 | Observational study with computational modeling |
Citations in the library
Cites 23
- Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial Journal of Psychopharmacology November 30, 2016
- Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance Psychopharmacology July 7, 2006
- Psilocybin with psychological support for treatment-resistant depression: an open-label feasibility study. The Lancet Psychiatry May 17, 2016
- Trial of Psilocybin versus Escitalopram for Depression New England Journal of Medicine April 14, 2021
- Single-Dose Psilocybin for a Treatment-Resistant Episode of Major Depression. New England Journal of Medicine November 3, 2022
and 18 more in the library