Early-onset psychosis (EOP) are a heterogeneous group, with high diagnostic stability for schizophrenia and bipolar disorder, in contrast to the lack of diagnostic stability of other EOP.

We recruited 24 adolescents consecutively admitted, who presented a first psychotic episode, in the adolescent psychiatric unit of the Gregorio Marañón General Hospital in Madrid, between May 2002 and May 2003, for a two year follow-up. Only one was lost at the two-year assessment.

Diagnosis of the psychotic disorders was assessed using the Kiddie-Sads-Present and Lifetime Version (K-SADS-PL).

The agreement between the baseline and the one-year follow-up diagnoses was 54.2%. Positive Predictive Value (PPV) was 100% for schizophrenia and depression with psychotic features, and 71.4% for bipolar disorder, while only 50.0% for schizo-affective disorder and 16.7% for psychosis NOS. From the one-year to the two-year follow-up, only one patient changed the diagnosis, so the agreement was 95.7%.

Eight patients were diagnosed with schizophrenia at the follow-up, but only four of them had received this diagnosis at the baseline assessment. The diagnosis of bipolar disorder was given at the follow-up to eight patients, from whom only four subjects received this diagnosis at baseline.

The results of the our longitudinal study on diagnostic stability support the Kraepelinean distinction between dementia praecox and manic-depressive psychosis.