Background: Depression is a frequent condition in early psychosis. Therefore, early detection instruments should distinguish depression from beginning psychosis.
Aims: To examine whether basic symptoms, i.e. subtle subjective deficits, differ between participants suffering from a potential prodrome (n=146), first-episode schizophrenia (n=153) and non-psychotic depression (n=115).
Method: Basic symptoms were assessed with the Schizophrenia Proneness Instrument.
Results: The prodrome and schizophrenia groups did not differ in level of basic symptoms but both had higher levels than the depression group. DSM-IV depression was frequent in those suffering from a potential prodrome (38%) and first-episode schizophrenia (21%). In both groups, participants with and without depression did not differ in basic symptoms. In multivariate analyses, consideration of current depression generally facilitated correct group classification, except for participants suffering from both a potential prodrome and depression.
Conclusions: Cognitive basic symptoms distinguished well between all three groups. However, identification of persons suffering from a potential prodrome might be enhanced by considering current affective status.