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The findings suggest the need for early identification and rapid treatment. “It is important to diagnose new cases of schizophrenia and bipolar disorder as soon as possible and to initiate treatment without delay, because prolonged psychosis without treatment is associated with a worse prognosis,” wrote Marie Stefanie Kejser Starzer, M.D., and colleagues at Copenhagen University Hospital.
Starzer and colleagues analyzed data from the Danish Psychiatric Central Research Register, which has registered all inpatient psychiatric treatment since 1969 and outpatient treatment since 1995.
The study population consisted of 6,788 patients who received a diagnosis of substance-induced psychosis over a 20-year period and who did not have any previous record of treatment for schizophrenia spectrum disorders or bipolar disorder. Ten comparison subjects were selected for each case subject, matched on sex, year, and month of birth, and being alive at the date of the incident substance-induced psychosis of the corresponding case subject.
The case subjects were followed up from incident substance-induced psychosis, and comparison subjects from their corresponding match date, until the first occurrence of schizophrenia or bipolar disorder or until death, migration, or Aug. 14, 2014, whichever came first.
A total of 32.2% of all patients with substance use-induced psychosis converted to either schizophrenia or bipolar disorder. In addition to cannabis use, self-harm after a substance-induced psychosis was significantly linked to a higher risk of converting to both schizophrenia and bipolar disorder. Young age was associated with a higher risk of conversion to schizophrenia; the risk was highest for those in the range of 16 to 25 years.
Fifty percent of conversions to schizophrenia occurred within 3.1 years, and 50% of conversions to bipolar disorder occurred within 4.4 years.
“Based on the different risk factors identified in different analyses and the overall conversion rate of 32.2%, it seems most reasonable to suggest that all patients with a substance-induced psychosis should be offered follow-up,” the authors stated. Follow-up from incidence of substance-use induced psychosis should be at least two years, they wrote.
For related information, see the Psychiatric News article “Cannabidiol May Benefit Patients With Early Psychosis, Cannabis Misuse.”
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