Do hallucinogens cause residual neuropsychological toxicity?

Introduction

Hallucinogenic drugs of botanical origin such as psilocybin, DMT, and mescaline have a long history of use, and over the past decades a broad array of synthetic analogues including LSD and MDMA have become widely used. Public health surveys in the 1980s and 1990s documented rising experimental and recreational use among adolescents and young adults, which has fuelled concern about potential long-term adverse effects. Clinical and editorial accounts have been sharply divided, with some authors warning of lasting personality deterioration, chronic psychosis, or organic brain syndromes after repeated exposure, while others have reported low rates of prolonged adverse reactions when drugs were administered in controlled settings. To address this controversy, Halpern and colleagues conducted a systematic review of studies in which formal neuropsychological tests were administered to users of LSD or other hallucinogens. The stated aim was to evaluate the evidence for residual neuropsychological toxicity attributable to hallucinogen use, and to identify methodological weaknesses in the existing literature that limit causal inference and interpretation.