[Cannabis and psychosis--a review]

The present review focuses on articles dealing with clinical or epidemiological studies on the association between cannabis use and psychoses. Included are all articles published since 1990 that were located by a Medline or Psyclit data-base research and those earlier articles that are needed for a correct understanding of studies published during the index episode. The three main topics found are 1) is there evidence for a so called cannabis psychosis 2) do cannabis users exhibit a higher risk of developing a psychotic disorder or 3) does its use worsen the course in established schizophrenia spectrum disorders. The review concludes that very high doses of cannabis can induce a brief psychosis but that this condition is extremely rare. Therefore, such a diagnosis should only be made after careful exclusion of other etiologies. The actual evidence regarding the impact of cannabis use on persons vulnerable to psychosis is not conclusive. Cannabis use seems to worsen the course of schizophrenia spectrum disorders. Adolescents run a higher risk from using cannabis than older people. They should be strongly advised not to indulge in such behaviour.