Non-psychotic psychiatric disorder and subsequent risk of schizophrenia

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Abstract
Background: Those with schizophrenia often give a history of premorbid non-psychotic psychiatric disorder.Aims: To investigate the association between non-psychotic psychiatric disorders and the later development of schizophrenia.Method: Men aged 18 or 19 years, conscripted to the Swedish army in 1970 (n=50 054) were linked to the Swedish National Psychiatric Case Register.Results: There was an increased risk of schizophrenia in those with ICD–8 diagnoses of neurosis (OR=4.6,95% CI 3.2–6.9), personality disorder (OR=8.2, 95% CI 5.4–12.3), alcohol abuse (OR=5.5, 95% CI 1.7–17.5) or substance abuse (OR=14.0, 95% CI 7.8–25.0) at age 18. Of those who developed schizophrenia, 38% (95% CI 32–45) received a diagnosis of non-psychotic psychiatric disorder at age 18. Only those with personality disorder had a significantly increased risk of schizophrenia (OR=2.4, 95% CI 1.1–5.2) with onset after age 23.Conclusions: Personality factors could represent an underlying vulnerability to schizophrenia. Other diagnoses occurring before schizophrenia may reflect a prodromal phase of the illness.