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The acute effects of synthetic intravenous Δ9-tetrahydrocannabinol on psychosis, mood and cognitive functioning
Published online by Cambridge University Press: 01 April 2009
Abstract
Recent work suggests that heavy use of cannabis is associated with an increased risk of schizophrenia-like psychosis. However, there is a dearth of experimental studies of the effects of the constituents of cannabis, such as Δ9-tetrahydrocannabinol (THC). In a study of intravenous (i.v.) synthetic THC in healthy humans, we aimed to study the relationship of the psychotic symptoms induced by THC to the consequent anxiety and neuropsychological impairment.
Twenty-two healthy adult males aged 28±6 years (mean±s.d.) participated in experimental sessions in which i.v. THC (2.5 mg) was administered under double-blind, placebo-controlled conditions. Self-rated and investigator-rated measurements of mood and psychosis [the University of Wales Institute of Science and Technology Mood Adjective Checklist (UMACL), the Positive and Negative Syndrome Scale (PANSS) and the Community Assessment of Psychic Experiences (CAPE)] were made at baseline and at 30, 80 and 120 min post-injection. Participants also completed a series of neuropsychological tests [the Rey Auditory Verbal Learning Task (RAVLT), Digit Span, Verbal Fluency and the Baddeley Reasoning Task] within 45 min of injection.
THC-induced positive psychotic symptoms, and participant- and investigator-rated measurements of these were highly correlated. Participants showed an increase in anxiety ratings but there was no relationship between either self- or investigator-rated positive psychotic symptoms and anxiety. THC also impaired neuropsychological performance but once again there was no relationship between THC-induced positive psychotic symptoms and deficits in working memory/executive function.
These findings confirm that THC can induce a transient, acute psychotic reaction in psychiatrically well individuals. The extent of the psychotic reaction was not related to the degree of anxiety or cognitive impairment.
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