Cognitive Deficits in Psychotic Disorders: A Lifespan Perspective

Abstract

Individuals with disorders that include psychotic symptoms (i.e. psychotic disorders) experience broad cognitive impairments in the chronic state, indicating a dimension of abnormality associated with the experience of psychosis. These impairments negatively impact functional outcome, contributing to the disabling nature of schizophrenia, bipolar disorder, and psychotic depression. The robust and reliable nature of cognitive deficits has led researchers to explore the timing and profile of impairments, as this may elucidate different neurodevelopmental patterns in individuals who experience psychosis. Here, we review the literature on cognitive deficits across the life span of individuals with psychotic disorder and psychotic-like experiences, highlighting the dimensional nature of both psychosis and cognitive ability. We identify premorbid generalized cognitive impairment in schizophrenia that worsens throughout development, and stabilizes by the first-episode of psychosis, suggesting a neurodevelopmental course. Research in affective psychosis is less clear, with mixed evidence regarding premorbid deficits, but a fairly reliable generalized deficit at first-episode, which appears to worsen into the chronic state. In general, cognitive impairments are most severe in schizophrenia, intermediate in bipolar disorder, and the least severe in psychotic depression. In all groups, cognitive deficits are associated with poorer functional outcome. Finally, while the generalized deficit is the clearest and most reliable signal, data suggests specific deficits in verbal memory across all groups, specific processing speed impairments in schizophrenia and executive functioning impairments in bipolar disorder. Cognitive deficits are a core feature of psychotic disorders that provide a window into understanding developmental course and risk for psychosis.

Keywords: Bipolar Disorder; Cognitive Impairment; Depression; Development; Psychosis; Schizophrenia.

Figure 1:

Estimated general cognitive impairment across the life span in schizophrenia, psychotic bipolar disorder, and psychotic depression. Effect size estimates based on studies presented in this review (e.g. Mollon & Reichenberg, 2017; Seidman et al., 2016; Heinrichs & Zakzanis, 1998; Mesholam-Gately et al., 2009; Daban et al., 2006; Hill et al., 2013; Martinez-Aran et al., 2004; Schatzberg et al., 2000). No data is currently available for premorbid or ultra-high risk psychotic depression. Childhood+ = children who develop disorder; UHR+ = ultra high risk individuals who develop disorder.

Figure 2:

Illustration of cognitive deficits in MDD patients with and without psychotic symptoms. While non-psychotic MDD patients demonstrate deficits in cognition, those with psychotic symptoms exhibit even greater deficits in all areas of cognition. This pattern suggest that the presence of psychosis contributes to greater cognitive impairment. Estimates based on data from Bora et al., 2013; Rock et al., 2014; Zaninotto et al., 2015