Psychosis is typically preceded by a prodrome, which begins with nonspecific symptoms like anxiety and depression before more specific negative and attenuated positive symptoms emerge. Prospective diagnostic criteria, developed from retrospective studies, show high reliability in research settings. Individuals assessed as at clinical high risk (CHR) are five to seven times more likely to progress to psychosis than those not at risk, and they also experience functional and cognitive impairment and distress. CHR diagnosis rates are low in general epidemiology studies, supporting validity, but substantially higher in clinical epidemiology studies, indicating CHR is an important but often overlooked clinical entity. Several areas needing additional research are identified.
Youth at clinical high-risk for psychosis report more lifetime, past-six-month, and baseline cannabis use than healthy controls, along with greater frequency, severity, and rates of cannabis use disorder. Among high-risk youth, those who use cannabis show higher baseline grandiosity and lower social anhedonia at 12 months. Cannabis use severity was unrelated to clinical status at two years and did not distinguish those who later developed psychosis from those who did not. The small number of cannabis users in the high-risk group limited statistical power.