Evolution of first episode psychosis diagnoses and health service use among young Māori and non-Māori-A New Zealand national cohort study

Aims: The validity of diagnostic classification in early psychosis has important implications for early intervention; however, it is unknown if previously found disparities between Māori (Indigenous people of New Zealand) and non-Māori in first episode diagnoses persist over time, or how these differences impact service use.

Methods: We used anonymized routine mental health service data and a previously established cohort of over 2400 13-25-year-old youth diagnosed with FEP between 2009 and 2012, to explore differences in diagnostic stability of psychosis diagnoses, comorbid (non-psychosis) diagnoses, and mental health service contacts between Māori and non-Māori in the five-year period following diagnosis.

Results: Differences in schizophrenia and affective psychosis diagnoses between Māori and non-Māori were maintained in the five-year period, with Māori being more likely to be diagnosed with schizophrenia (51% vs. 35%), and non-Māori with bipolar disorder (28% vs. 18%). Stability of diagnosis was similar (schizophrenia 75% Māori vs. 67% non-Maori; bipolar disorder 55% Māori vs. 48% non-Māori) and those with no stable diagnosis at FEP were most likely to move towards a schizophrenia disorder diagnosis in both groups. Māori had a lower rate of diagnosed co-morbid affective and anxiety symptoms and higher rates of continued face to face contact and inpatient admission across all diagnoses.

Conclusions: Indigenous differences in schizophrenia and affective psychosis diagnoses could be related to differential exposure to socio-environmental risk or assessor bias. The lower rate of co-morbid affective and anxiety disorders indicates a potential under-appreciation of affective symptoms in Māori youth with first episode psychosis.