Cognitive decline and impairment in schizophrenia spectrum disorders reconsidered

This study applied an algorithm developed to identify schizophrenia spectrum disorder patients with probable decrements between estimated premorbid and current cognitive ability (Keefe et al., 2005). Cognitive trajectories and associated functional status were examined in patients and control participants.

Patients with schizophrenia or schizoaffective disorder (n = 139) and control participants (n = 63) completed measures of verbal and working memory, processing speed, verbal fluency, reading ability and non-verbal reasoning. A predicted cognitive composite score was generated using control participants' parental education and reading scores, consistent with methods in Keefe et al. (2005), and compared to current performance. Three performance trajectory profiles were identified: decrement, stable, and increment. Functionality and clinical status were assessed with the Multidimensional Scale of Independent Functioning (MSIF) and the Positive and Negative Syndrome Scale (PANSS).

Approximately 60% (n = 83) of patients demonstrated a decrement trajectory, 16% (n = 22) demonstrated an increment trajectory, and 24% (n = 34) demonstrated a stable trajectory. Patients with decrement profiles were significantly more symptomatic (negative) and functionally impaired (MSIF) than those with increment profiles. Patients with increment and normal-range performance profiles remained functionally deficient relative to controls.

Schizophrenia and schizoaffective patients meeting psychometric criteria for cognitive decline relative to estimated premorbid levels are common in the outpatient population but may occur less frequently than earlier estimates suggest. Minorities with stable and improved performance profiles also exist, show clinical and functional advantage relative to more typical patients, but underperform healthy controls.