Concordance of positive and negative symptoms in coaffected sib-pairs with schizophrenia

Positive and negative symptom (NGS) dimensions were examined for their concordance in 46 coaffected schizophrenic sib-pairs. Results showed that the symptom dimensions of negative symptoms (NGS), delusion-hallucination (DHS), and thought disorganization (TDS) could be formulated. Discrete genetic endowment of these three symptom dimensions was not found as shown by the low concordance in sib pair analysis (kappa = 0.20-0.30). Thirty-seven pairs (80.4%) and 21 pairs (45.7%) had liability, defined by the presence of NGS in any one member of the coaffected sib-pairs, of NGS of "any degree", and of "severe degree" in 46 sib-pairs, respectively. Both groups had high prevalence (59.1-81.0%) of positive symptoms. Another 9 (19.6%) and 25 (54.3%) pairs had no liability of NGS of "any degree" or of "severe degree" out of 46 sib-pairs, respectively. These two groups had high concordance (kappa = 0.45-1.00) of TDS or DHS between coaffected sib-pairs. Based on the results, it is hypothesized that schizophrenia, as defined by DSM-III-R, may consist of two subtypes: one has liability of NGS and a high prevalence of positive symptoms, while the other has only positive symptoms.