Negative symptoms in depressed and schizophrenic patients: how do they differ?

BACKGROUND: The present study evaluated differences in negative symptoms between schizophrenic and depressive patients and investigated whether a consideration of the nature of negative symptoms (enduring vs. nonenduring) can help to improve their specificity for schizophrenia.
METHOD: Patients enrolled in the study were consecutively hospitalized with an acute exacerbation of schizophrenia (N = 33) or major depressive disorder (N = 43) (DSM-IV). Negative and depressive symptoms were assessed with the Scale for the Assessment of Negative Symptoms (SANS) and the Montgomery-Asberg Depression Rating Scale, respectively. Duration of negative symptoms was assessed through a semistructured interview with the patients and their closest relatives. On the basis of the assessed duration of symptoms, negative symptoms were categorized as enduring or nonenduring.
RESULTS: Analyses revealed high SANS ratings for both diagnostic groups. Negative symptoms in depressive patients (p =.01), but not in schizophrenic patients, were significantly associated with the presence or the emergence of depressive symptoms. The prevalence of enduring negative symptoms was significantly higher in schizophrenic patients than in depressive patients (p <.01). A consideration of enduring negative symptoms significantly increased the discriminative power of negative symptoms for schizophrenia (p =.02).
CONCLUSION: The present findings suggest that negative symptoms in most depressive patients are just an epiphenomenon of depressive symptoms and can be distinguished from schizophrenic negative symptoms.