Are negative symptoms associated with functioning deficits in both schizophrenia and nonschizophrenia patients? A 10-year longitudinal analysis.

The current analyses assess the functional correlates of negative symptoms across diagnoses and across time to assess the appropriateness of a dimensional approach to the study of negative symptoms--specifically, whether negative symptoms should be studied as a single construct across diagnostic groups. Seventy-two schizophrenia/schizoaffective, 36 other psychotic, and 42 nonpsychotic depressed patients were recruited at index hospitalization and were followed up 4.5, 7.5, and 10 years later. At each followup assessment, data were collected on symptoms and adaptive and cognitive functioning. Analyses indicated that negative symptoms showed some similar functional associates in all three diagnostic groups, although results were strongest for the schizophrenia spectrum patients. Negative symptoms at the 10-year followup were associated with different patterns of social deficits prior to index hospitalization in the three diagnostic groups. The data provide some support for a dimensional approach to the study of mental illness, with negative symptoms associated with deficits across diagnosis, but also provide evidence of some diagnostic differences.