Historic psychedelic drug trials and the treatment of anxiety disorders

In this paper, we systematically review literature from 1940 to 2000 relating to the combined use of psychological therapies and psychedelic drugs in the treatment of ICD-10 anxiety disorders.

The databases Ovid MEDLINE(R), PsycINFO, and Multidisciplinary Association for Psychedelic Studies (MAPS) were searched for case reports and trials involving humans in the treatment of ICD-10 anxiety and related disorders. Twenty-four studies are described; four describe anxiety symptoms in diverse patient groups, 14 studies describe historic diagnoses that usefully correspond with ICD-10 anxiety disorders, six studies pooled results or failed to detail results specific to contemporary ICD-10 anxiety disorders. Two of the 24 studies reported are individual case reports while two of them were inadequate in terms of the reporting of outcome measures. Thus 20 studies were ultimately included in the summary analysis.

Three of the 20 studies reviewed described improvements in anxiety by standardized measures (p < .05) and two studies found that this effect was dose related. Of the 20 studies included in the final analysis, 94 of 145 (65%) cases of "psychoneurotic anxiety reaction" as defined by Diagnostic and Statistical Manual of Mental Disorders-I showed improvement that ranged from moderate improvement to full recovery. Despite methodological inadequacies, the results from previous studies are encouraging and should be used to guide and inform further investigation.

The majority of studies indicate that a combination of psychedelic drug administration and psychological therapy was most beneficial. We found no study suggesting that the pharmacological action of psychedelic drugs in isolation is sufficient.