In patients with schizophrenia, the connection between depression and cognitive performance has not been well studied, and the link between the presence of depressive symptoms and functional impairment in patients with schizophrenia is a contested one.[Harvey, 2011] Somewhat paradoxically, some have associated depressive symptoms with better social and cognitive performance.[Rieckmann et al., 2005] Taken together, though, the weight of evidence suggests that mood symptoms in patients with schizophrenia are associated with greater real-world disability.[Harvey, 2011]
References:
Harvey PD. Mood symptoms, cognition, and everyday functioning in major depression, bipolar disorder, and schizophrenia. Innov Clin Neurosci 2011; 8 (10): 14–18.
Rieckmann N, Reichenberg A, Bowie CR, et al. Depressed mood and its functional correlates in institutionalized schizophrenia patients. Schizophr Res 2005; 77 (2–3): 179–187.