Diagnostic conversion following admission for a first-episode substance induced psychosis: A four-year retrospective cohort study

Master Thesis


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Background: Substance-induced psychotic disorder (SIPD) is prevalent in South Africa, yet there is a paucity of research regarding its longitudinal course, with studies finding that diagnostic conversion occurs often, mostly to schizophrenia (SCZ). Aim: We examined the rate of, and factors associated with, diagnostic conversion in first-episode SIPD to primary, non-substance-related mental disorders. Setting: Adult inpatients with a diagnosis of first-episode SIPD discharged between 2012 to 2014 from Valkenberg psychiatric hospital, Cape Town. Methods: We conducted a retrospective cohort study of first-episode patients discharged from hospital, followed-up for a four-year period. We used survival analysis and Cox-proportional hazard regression to determine factors associated with diagnostic conversion to a primary mental disorder. Results: Of the sample of 225 patients, the majority were young, male and polysubstance users. Diagnostic conversion occurred in 26.2%, the majority within 3 years - 71.2% to SCZ-spectrum disorders and 28.8% to major affective disorders. In the adjusted analysis, diagnostic conversion remained significantly associated with male sex (HRadj=1.85, 95% CI=1.00– 3.42, p=0.045) and greater length of index admission (HRadj=1.02, 95% CI=1.01 – 1.04, p=0.006). Compared to nonconverters, significant associations with conversion to SCZ-spectrum disorders were male sex and length of index admission. Conversions to both SCZ-spectrum and major affective disorders were significantly associated with number of re-admissions during follow-up. Conclusion: Diagnostic conversion occurred in a substantial proportion of SIPD cases, often to SCZ. This warrants enhanced follow-up of high-risk cases, with attention to indicators such as sex and length of index hospitalisation.