Cannabis and psychotic illness.

Area of Science:

• Psychiatry
• Clinical Psychology
• Neuroscience

Background:

• Psychotic symptoms are sometimes associated with cannabis use.
• Differentiating acute cannabis intoxication from chronic psychotic disorders is clinically important.
• Cannabis-induced psychosis is a diagnostic consideration in patients presenting with psychosis.

Purpose of the Study:

• To investigate the short-term and medium-term course of psychotic symptoms in patients with cannabis-positive urine tests.
• To compare the symptom profiles of cannabis-using patients with psychotic symptoms to a control group of psychotic patients without cannabis use.
• To assess whether symptoms consistent with cannabis-induced psychosis persist over time.

Main Methods:

• Prospective assessment of in-patients with psychotic symptoms and cannabis-positive urine.
• Use of the Present State Examination (PSE) at one week, one month, and six months post-admission.
• Comparison with a control group of concurrently admitted psychotic patients with drug-free urine analyses.

Main Results:

• At one week, significant differences between groups were observed in specific psychotic symptoms including altered perception, thought insertion, auditory hallucinations, and delusions.
• One symptom, delayed sleep, differed at one month, with no significant differences found at six months.
• The symptom cluster at one week aligns with acute cannabis intoxication; chronic cannabis-induced psychosis was not identified.

Conclusions:

• The findings suggest that psychotic symptoms in this cohort were primarily indicative of acute cannabis intoxication, with rapid resolution.
• The study cautions that the label 'cannabis-induced psychosis' might obscure a diagnosis of underlying paranoid schizophrenia.
• A short-lived psychotic episode can occur following cannabis intoxication, but chronic cannabis-induced psychosis was not evident in this study.