The impact of cannabis and stimulant disorders on diagnostic stability in psychosis.

BACKGROUND: Substance abuse adds to diagnostic uncertainty in psychosis and may increase the risk of transition from brief and affective psychoses to schizophrenia. This study examined whether comorbid substance disorder was associated with diagnostic instability and progression from other psychosis diagnoses to schizophrenia and whether effects differed for cannabis and stimulant-related disorders. METHOD: We identified 24,306 individuals admitted to hospital with an ICD-10 psychosis diagnosis between 2000 and 2011. We examined agreement between initial diagnosis and final diagnosis over 2-5 years and predictors of diagnostic change toward and away from a final diagnosis of schizophrenia. RESULTS: Nearly half (46%) of participants with initial brief, atypical, or drug-induced psychoses were later diagnosed with schizophrenia. Persisting illicit drug disorders did not increase the likelihood of progression to schizophrenia (OR = 0.97; 95% CI, 0.89-1.04) but increased the likelihood of revision of index psychosis diagnosis away from schizophrenia (OR = 1.55; 95% CI, 1.40-1.71). Cannabis disorders predicted an increased likelihood of progression to schizophrenia (OR =1.12; 95% CI, 1.01-1.24), while stimulant disorders predicted a reduced likelihood (OR = 0.81; 95% CI, 0.67-0.97). Stimulant disorders were associated with greater overall diagnostic instability. CONCLUSIONS: Many people with initial diagnoses of brief and affective psychoses are later diagnosed with schizophrenia. Cannabis disorders are associated with diagnostic instability and greater likelihood of progression to schizophrenia. By contrast, comorbid stimulant disorders may be associated with better prognosis in psychosis, and it may be important to avoid premature closure on a diagnosis of schizophrenia when stimulant disorders are present.

Stimulant and other substance use disorders in schizophrenia: prevalence, correlates and impacts in a population sample.

OBJECTIVES: Stimulants may worsen psychotic symptoms but there is limited evidence about the impact of stimulant abuse in people with schizophrenia. This study examined the prevalence and correlates of stimulant and other drug disorders in a population-based sample of people with schizophrenia, examining associations with frequent service use, physical health comorbidities and accommodation instability. METHODS: New South Wales (NSW) hospital, community mental health and emergency department data were used to examine health service contact over 5 years in 13,624 people with a diagnosis of schizophrenia. Associations of stimulant disorders were examined with multinomial logistic regression, comparing people with no substance disorders to those with cannabis disorders, stimulant disorders or both. RESULTS: Of people with schizophrenia, 51% had substance disorders, including 14% with stimulant disorders. Stimulant disorders were more common in young adults and in urban areas, less common in migrants, and unrelated to initial social disadvantage. More than 80% of those with stimulant disorders also had cannabis disorders. Service use and harms were most common in this group, including frequent mental health admissions (59%), frequent emergency department presentations (52%), admissions with injury or self-harm (44%), infectious disease diagnoses (22%), multiple changes of residence (61%), movement to more disadvantaged locations (42%) and periods of homelessness (18%). People with stimulant disorders alone had higher rates of self-harm, infectious disease and non-mental health admissions than people with cannabis disorders alone. CONCLUSIONS: Stimulant disorders occur in people with schizophrenia and in first-episode psychosis at rates more than 10 times that of the broader population. Stimulant disorders are likely to worsen the burden of psychosis, and strategies are needed to engage and support the highly disadvantaged group of people with schizophrenia who have cannabis and stimulant disorders.

Cannabis and stimulant disorders and readmission 2 years after first-episode psychosis.

BACKGROUND: Few studies have examined the impact of stimulant use on outcome in early psychosis. Ceasing substance use may lead to positive outcomes in psychosis. AIMS: To examine whether baseline cannabis or stimulant disorders and ongoing drug use predict readmission within 2 years of a first psychosis admission. METHOD: Predictors of readmission were examined with Cox regression in 7269 people aged 15-29 years with a first psychosis admission. RESULTS: Baseline cannabis and stimulant disorders did not predict readmission. A stimulant disorder diagnosis prior to index psychosis admission predicted readmission, but a prior cannabis disorder diagnosis did not. Ongoing problem drug use predicted readmission. The lowest rate of readmission occurred in people whose baseline drug problems were discontinued. CONCLUSIONS: Prior admissions with stimulant disorder may be a negative prognostic sign in first-episode psychosis. Drug use diagnoses at baseline may be a good prognostic sign if they are identified and controlled.