Cannabis use has been found to co-exist with a range of mental health symptoms and disorders (a concurrence referred to hereafter as co-morbidity). Large-scale epidemiological surveys have found higher rates of psychotic, affective, anxiety, and behavioural disorders among individuals with substance use disorders than in the general population (Degenhardt, Hall & Lynskey, 2001; Farrell et al., 2001; Merikangas et al., 1998). The majority of individuals seen at publically-funded mental health services have psychosis (including schizophrenia), bipolar disorder, or severe personality disorder, especially borderline personality disorder. Though there has been a dearth of studies on the latter, there have been several attempts to develop treatments for cannabis use for the former conditions (Edwards et al., 2006; Barrowclough et al., 2001; Baker et al, 2006; Kavanagh et al., 2002). Recent Australian studies have found cannabis use in individuals with psychosis to be significantly greater than have comparable international studies (Wade et al., 2006; Wade et al., 2007; Hinton, Edwards & Elkins, 2008) in a similar population of patients with recent-onset psychosis.
Source: www.npic.au 2009 Management of Cannabis and Related Disorders