Does familiality predispose to both emergence and persistence of psychosis? A follow-up study.

BACKGROUND: It as been suggested that in schizophrenia an association exists between family history of schizophrenia and poor outcome on the one hand, and family history of affective disorders and good outcome on the other.
METHOD: We tested for associations between four-year outcome and familial loading for psychotic disorders in a mixed sample of 150 consecutively admitted patients with functional psychosis (schizophrenia, psychotic affective disorders, other psychotic disorders) of recent onset. For each proband, a familial loading score for (i) broadly defined psychotic disorder, (ii) schizophrenia, and (iii) affective disorder was calculated using information on relatives obtained through the Family History Research Diagnostic Criteria method and direct interviews of relatives with the Schedule for Affective Disorders and Schizophrenia.
RESULTS: In our sample of psychotic patients, familial loading for psychotic disorder predicted persistent negative symptoms over the follow-up period (OR 1.5; 95% CI 1-2.2), especially in schizophrenia, and was also associated with more time hospitalised (P < 0.05) [corrected], and more social disability at follow-up (P < 0.05). Greater familial loading for schizophrenia predicted a greater likelihood of non-recovery (OR 2.2; 95% CI 1.1-4.4) and a greater likelihood to have had persistent negative symptoms over the follow-up period (OR 1.7; 95% CI 0.9-3.1). No association was found between outcome and familial loading for affective disorder.
CONCLUSIONS: We conclude that familial loading may be a continuous risk factor for some dimensions of clinical outcome in the functional psychoses. This suggests that there is a continuum of genetic liability not only to the emergence of psychotic illness, but also the subsequent chronicity of the disorder.