Long-term Changes in Cognitive Functioning in Individuals With Psychotic Disorders

Importance

It remains uncertain whether people with psychotic disorders experience progressive cognitive decline or normal cognitive aging after first hospitalization. This information is essential for prognostication in clinical settings, deployment of cognitive remediation, and public health policy.

Objective

To examine long-term cognitive changes in individuals with psychotic disorders and to compare age-related differences in cognitive performance between people with psychotic disorders and matched control individuals (ie, individuals who had never had psychotic disorders).

Design, Setting, and Participants

The Suffolk County Mental Health Project is an inception cohort study of first-admission patients with psychosis. Cognitive functioning was assessed 2 and 20 years later. Patients were recruited from the 12 inpatient facilities of Suffolk County, New York. At year 20, the control group was recruited by random digit dialing and matched to the clinical cohort on zip code and demographics. Data were collected between September 1991 and July 2015. Analysis began January 2016.

Main Outcomes and Measures

Change in cognitive functioning in 6 domains: verbal knowledge (Wechsler Adult Intelligence Scale–Revised vocabulary test), verbal declarative memory (Verbal Paired Associates test I and II), visual declarative memory (Visual Reproduction test I and II), attention and processing speed (Symbol Digit Modalities Test–written and oral; Trail Making Test [TMT]–A), abstraction-executive function (Trenerry Stroop Color Word Test; TMT-B), and verbal fluency (Controlled Oral Word Association Test).

Results

A total of 705 participants were included in the analyses (mean [SD] age at year 20, 49.4 [10.1] years): 445 individuals (63.1%) had psychotic disorders (211 with schizophrenia spectrum [138 (65%) male]; 164 with affective psychoses [76 (46%) male]; 70 with other psychoses [43 (61%) male]); and 260 individuals (36.9%) in the control group (50.5 [9.0] years; 134 [51.5%] male). Cognition in individuals with a psychotic disorder declined on all but 2 tests (average decline:d = 0.31; range, 0.17-0.54; allP < .001). Cognitive declines were associated with worsening vocational functioning (Visual Reproduction test II:r = 0.20; Symbol Digit Modalities Test–written:r = 0.25; Stroop:r = 0.24;P < .009) and worsening negative symptoms (avolition: Symbol Digit Modalities Test–written:r = −0.24; TMT-A:r = −0.21; Stroop:r = −0.21; allP < .009; inexpressivity: Stroop:r = −0.22;P < .009). Compared with control individuals, people with psychotic disrders showed age-dependent deficits in verbal knowledge, fluency, and abstraction-executive function (vocabulary: β = −0.32; Controlled Oral Word Association Test: β = −0.32; TMT-B: β = 0.23; allP < .05), with the largest gap among participants 50 years or older.

Conclusions and Relevance

In individuals with psychotic disorders, most cognitive functions declined over 2 decades after first hospitalization. Observed declines were clinically significant. Some declines were larger than expected due to normal aging, suggesting that cognitive aging in some domains may be accelerated in this population. If confirmed, these findings would highlight cognition as an important target for research and treatment during later phases of psychotic illness.