The acute effects of synthetic intravenous Delta9-tetrahydrocannabinol on psychosis, mood and cognitive functioning

Psychol Med. 2009 Oct;39(10):1607-16. doi: 10.1017/S0033291709005522. Epub 2009 Apr 1.

Abstract

Background: 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 Delta9-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.

Method: 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.

Results: 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.

Conclusions: 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Affect / drug effects*
  • Arousal / drug effects
  • Cognition / drug effects*
  • Double-Blind Method
  • Dronabinol / pharmacokinetics
  • Dronabinol / pharmacology*
  • Humans
  • Injections, Intravenous
  • Male
  • Psychiatric Status Rating Scales
  • Psychological Tests
  • Psychoses, Substance-Induced / etiology*

Substances

  • Dronabinol