Cognitive decline sets in well before onset of psychosis but accelerates in third decade of illness: JAMA

A new study conducted by Katherine Jonas and team suggests that cognitive trajectories in schizophrenia matched both a neurodevelopmental and a neurodegenerative trend, resulting in a loss of 16 IQ points throughout the course of the study. The findings of this study were published in the Journal of American Medical Association - Psychiatry.

Schizophrenia is accompanied with significant cognitive abnormalities and has been classified as a neurodevelopmental as well as a neurodegenerative condition. However, it is unknown when deficiencies occur and how they alter during the course of the illness. As a result, this study was carried out in order to evaluate neurodevelopmental and neurodegenerative hypotheses of psychotic diseases by tracing cognition from elementary school through old age.

The data came from the Suffolk County Mental Health Project, which is a first-admission longitudinal cohort study of people with psychotic illnesses. Participants were drawn from Suffolk County's 12 inpatient psychiatric hospitals. This study looked at 428 people who had at least two estimations of their general cognitive ability. Data were gathered between September 1989 and October 2019, and analysis was placed between January 2020 and October 2021. All participants were in psychiatric hospitals for psychosis. Cognitive ratings for readmission were obtained from school and medical data. Neuropsychological testing was used to determine post onset cognitive scores at 6 month, 24 month, 20 year, and 25 year intervals.

The key findings of this study were as follow:

1. The mean (SD) age at psychosis start was 27 (9) years among the 428 people included in the study.

2. Cognitive change was seen in three stages: normal, decreasing, and worsening.

3. Cognition was steady during the first phase.

4. Those with schizophrenia began to experience cognitive deterioration at a rate of 0.35 intelligence quotient (IQ) points per year fourteen years before the beginning of psychosis, a much quicker drop than those with other psychotic diseases.

5. Both groups deteriorated at a rate of 0.59 IQ points per year 22 years after commencement.

In conclusion, cognitive decline occurred well before the onset of psychosis, suggesting that the opportunity for primary prevention is earlier than previously assumed. Secondary preventive opportunities occur in the third decade of disease, when cognitive deficits increase in people with schizophrenia and other psychotic illnesses.

Reference:

Jonas, K., Lian, W., Callahan, J., Ruggero, C. J., Clouston, S., Reichenberg, A., Carlson, G. A., Bromet, E. J., & Kotov, R. (2022). The Course of General Cognitive Ability in Individuals With Psychotic Disorders. In JAMA Psychiatry. American Medical Association (AMA). https://doi.org/10.1001/jamapsychiatry.2022.1142