Relationship between depressive and positive symptoms in schizophrenia

The aim of this study was to investigate the relationship between depressive and positive symptoms, two positive symptom using scales (PANSS and SAPS) in samples defined by three schizophrenic diagnostic systems (DSMIII-R, ICD9 and Langfeldt) at difference phases of the illness and in taking into account the negative and extrapyramidal symptoms and the doses of neuroleptics. With both scales, correlations between depressive and positive symptoms were significantly negative in two diagnostic subgroups (DSMIII-R and Langfeldt) in the acute phase. These correlations were also significant when negative symptoms, subjective extrapyramidal signs and the doses of neuroleptics were partialled out. Only the extrapyramidal physician's score was intercorrelated with positive and negative symptoms. Among the positive symptoms, 'conceptual disorganization' (or 'positive formal thought disorder') and 'suspiciousness/persecution' were especially correlated negatively with depression. At the post-acute phase or at the residual phase, no significant correlation between depressive and positive symptoms was found in any diagnostic subgroup. These results show the necessity of taking into account the phase of illness and the diagnostic criteria in order to study depression in schizophrenia.