Relationship between positive and negative symptoms of schizophrenia and schizotypal symptoms in nonpsychotic relatives

Background: Continuous rather than categorical measures of psychopathology may provide greater statistical power to detect susceptibility loci for sch izophrenia. However, it has not been established that the dimensions of sch izophrenic symptomatology and personality traits in nonpsychotic individual s share etiological factors. We therefore sought to clarify the relationshi p between positive and negative symptoms of schizophrenic probands acid dim ensions of schizotypy in their first-degree relatives. Methods: In the Roscommon Family Study, we examined the ability of positive and negative symptoms in probands to predict 7 factors of schizotypy in no npsychotic relatives using regression analysis. These consisted of positive , negative, and avoidant symptoms. odd speech; suspicious behavior; social dysfunction: and symptoms of borderline personality disorder. We examined 3 proband groups: schizophrenia (n=127): schizophrenia, simple schizophrenia , and schizoaffective disorder (n=178); and all nonaffective psychoses (n=2 16), and their nonpsychotic relatives (n=309, 477, and 584, respectively). Results; Positive symptoms in all noneffective psychoses probands predicted positive schizotypy (beta =0.1972, P=.0004). social dysfunction (beta =0.0 719 P=.0489),and borderline personality disorder symptoms (beta =0.1327. P= .0084) in relatives, while negative symptoms predicted negative schizotypy (beta =0.2069, P=.0002), odd speech (beta =0.2592, P=.0001), suspicious beh avior (beta =0.2749, P=.0001), and social dysfunction (beta=.2398, P=.0002) . Proband negative symptoms and borderline personality disorder symptoms in relatives in the schizophrenia. simple schizophrenia, and schizoaffective disorder group were inversely related (beta= -0.1185, P=.05), Conclusions: Positive and negative syInptoms in schizophrenia predict corre sponding schizotypal symptoms in relatives. This provides evidence that the se schizo phrenic symptom factors (1) are etiologically distinct from each other and (2) occur on an etiological continuum with their personality-base d counterparts.