We investigated whether psychosis risk symptoms predicted psychiatric service use using seven-year register follow-up data.

Our sample included 715 adolescents aged 15–18, referred to psychiatric care for the first time. Psychosis risk symptoms were assessed with the Prodromal Questionnaire (PQ) at the beginning of the treatment. We assessed the power of the overall PQ as well as its positive, negative, general, and disorganized psychosis risk symptom factors in predicting prolonged service use. Baseline psychiatric diagnoses (grouped into 7 categories) were controlled for. Based on both inpatient and outpatient psychiatric treatment after baseline, adolescents were divided into three groups of brief, intermittent, and persistent service use.

Stronger symptoms on any PQ factor as well as the presence of a mood disorder predicted prolonged service use. All of the PQ factors remained significant predictors when adjusted for baseline mood disorder and multimorbidity.

In a prospective follow-up of a large sample using comprehensive mental health records, our findings indicate that assessing psychosis risk symptoms in clinical adolescent settings at the beginning of treatment could predict long-term need for care beyond diagnostic information. Our findings replicate the previous findings that positive psychosis risk symptoms are unspecific markers of severity of psychopathology. Also psychosis risk symptoms of the negative, disorganization, and general clusters are approximately as strongly associated with prolonged psychiatric service use in the upcoming years.