Which levels of cognitive impairments and negative symptoms are related to functional deficits in schizophrenia?

Background: Negative symptoms and cognitive impairments predict difficulties in aspects of everyday functioning in schizophrenia, with little research to date attempting to determine if there are threshold levels of impairment required to predict the severity of functional deficits. Methods: People diagnosed with chronic schizophrenia (n = 821) were assessed with the MCCB and PANSS, and rated by high contact informants with SLOF. Negative symptoms of reduced emotional experience were specifically targeted for analysis because of their previously identified relationships with social outcomes. We identified patients with moderate negative symptoms (at least one PANSS item ≥4) versus less severe symptoms (PANSS items ≤3) and divided patients on the basis of a single latent-trait global cognition score (neuropsychologically normal vs neuropsychologically impaired; performance at or below 1.0 SD from the normative population mean, T = 40), then examined correlations between cognition, negative symptoms and everyday functioning in the groups with lower and higher negative symptoms and those with/without cognitive impairment. Results: Even low levels of negative symptoms were correlated with ratings of social functioning. Cognitive performance in the neuropsychologically normal range, in contrast, was not correlated with any aspects of everyday functioning while more impaired performance predicted greater functional impairments. Conclusions: Even minimal symptoms may be a target for clinical attention in the domains of negative symptoms, consistent with previous findings regarding social deficits in populations with modest negative symptoms (e.g., schizotypal personality disorder). Cognitive rehabilitation treatments might not improve social functioning if even low levels of negative symptoms (social amotivation) are present.