Abstract
Dear Editor
In view of the renewed interest in psychedelics in neuroscience and psychiatry, J.K. Larsen’s historical paper ‘Neurotoxicity and LSD treatment: a follow-up study of 151 patients in Denmark’ (History of Psychiatry 27(2): 172–189) about LSD therapy in the 1950–70s is very timely. However, we believe that the paper suffers from an inadequate discussion of the dataset, and that conclusions about ‘a substantial risk of long-term side-effects’ and LSD’s ‘obvious neurotoxic qualities’ are unjustified. Our main concerns are listed here:
1. Context
The medical reports reviewed by Larsen were written 15–30 years after the treatments had taken place, in order to serve as evidence for the Danish Government’s ‘LSD Tribunal’. This tribunal was contrived under a special law in April 1986 to offer compensations to patients who had been treated with LSD. The law employed a so-called ‘reverse burden of evidence’, which meant that LSD was identified as the cause of harm to the applicant – ‘unless it was most likely that the harm was due to another cause’. This retrospective evaluation of (alleged) harm, in the context of a compensatory incentive, clearly represents a major confounder and a weak basis on which to draw medical conclusions. It is also telling that the conclusions of the original publications on LSD therapy in Denmark reached predominantly positive conclusions about its potential (Geert-Joergensen, Hertz, Knudsen and Kristensen, 1964).
2. Set and setting
When reading Larsen’s paper, as well as the Danish-language original material from the book De Sprængte Sind (Larsen, 1985), quoting the original medical files, it is evident that the treatment regime used, in particular at Frederiksberg Hospital, conflicts with recommendations for good practice in clinical research with psychedelics (Grof, 1975; Johnson, Richards and Griffiths, 2008). None of the following factors, all known to ensure the safe use of psychedelics in therapy, were sufficiently addressed:
Careful pre-treatment screening: A wide range of diagnoses was allowed at Frederiksberg Hospital, including psychotic illness and ‘homosexuality’.
Consent and preparation: Patients were persuaded to take high doses of LSD and there is no evidence that they were carefully briefed about its effects, including how psychologically challenging the experiences can be, and how best to navigate such experiences.
Guiding/support during sessions: Patients at the Frederiksberg Hospital were often left alone during their LSD experiences, and integration work was not done, i.e. the therapists did not discuss with the patients what had occurred/arisen during their drug sessions. Importantly, none of the patients treated at Rigshospitalet, a treatment site where psychotherapy was an integrated part of the treatment regime, sought any compensation.
3. The drug
Some patients received up to 50 LSD sessions, were given doses up to 800 micrograms, and were given the drug in combination with other psychedelics. This approach is inconsistent with that of modern studies, where single session designs are common and doses of LSD typically do not exceed 200 micrograms.
4. Neurotoxicity
This term is used without definition or basis in the Larsen paper. The original material does not present any data on neurotoxicity and, to our knowledge, there is no evidence of psychedelic-induced neurotoxicity to humans, e.g. in terms of the integrity of serotonin neurotransmission (Erritzoe et al., 2011).
In our view, the conclusions of Dr Larsen’s paper are unjustified. The history of litigious campaigning and poor practices, relative to modern standards, raises serious questions about its representativeness. These factors may explain why the conclusions of Dr Larsen’s paper so starkly contrast with those of modern meta-analyses and clinical trials. Psychedelic drugs have a special tendency to polarize opinion. Just as we must be mindful of uncritical positive regard, so we should be suspicious of alarmist and/or moralist biases.