A new study has shown that relative to participants without a psychotic disorder, those diagnosed with a disorder were consistently impaired across all areas of cognitive (memory and thinking) ability measured. The comparison also suggested that declines in some cognitive areas might worsen with age.
This was as part of a cross- sectional comparison 20-years after diagnosis of their first psychotic episode.
Crucially, the study found that cognitive impairment of participants with a psychotic disorder was linked to their symptoms, particularly loss of interest in everyday activities, and also negative changes in their employment.
Academics from City, University of London, Icahn School of Medicine at Mount Sinai, New York, Stony Brook University, New York and others, conducted the study as part of the Suffolk County Mental Health Project in the United States. The project began in 1989 in order to find out what challenges people diagnosed with psychotic disorders may face throughout their lives.
Previous research has shown cognitive impairment to be a core feature of schizophrenia and is associated with poor social and vocational outcomes for those affected. However, little was previously known about how cognitive impairment may progress in the longer term in schizophrenia and other psychotic disorders, as studies beyond 10 years after first diagnosis are rare.
The study involved 445 participants who had been admitted to psychiatric inpatient units within Suffolk County. Participants came back to complete cognitive testing at two and 20 year follow-up after their first episode of psychosis. Participants undertook a range of tests which measured different aspects of their cognitive functioning, including their vocabulary knowledge, their ability to recount words from memory, memory of factual information and previous experiences, and ability to conceptualize across ideas and decision-making. They also took part in clinical interviews that assessed their symptom level and how well they were doing socially, as well as functionally in terms of vocation/ and employment.
Twenty years after their diagnosis, cognitive functioning of those with a psychotic disorder was compared with a group of non-psychotic participants from Suffolk County who were matched to them by gender and age.
Co-first author of the study, Dr Anne-Kathrin Fett, Senior Lecturer in Psychology at City, University of London, said:
Our study provides the first comprehensive picture of long-term cognitive changes and associated clinical and functional outcomes in psychotic disorders, and is an important step toward providing clarity on what challenges people with these disorders face in the community.
However, it is important to note that while there was a general downward trend, participants varied in terms of cognitive changes and some also achieved improvement over the follow-up period. We need to find out what can influence cognitive functioning positively. We do not yet have medication, but lifestyle changes may be able to improve cognition long-term to some extent.
Importantly replication and further studies will be necessary to offer directions for the development of strategies to help prevent the progressive deterioration of cognitive functioning in later stages of psychotic illness."
The study also found that cognitive impairment across schizophrenia spectrum disorders and other psychotic conditions, including psychotic bipolar disorder, major depression with psychosis and substance induced psychosis, had similar trajectories of cognitive decline over an 18-year period since measured two years after the first diagnosis.
Fett, A-K., et al. (2019) Long-term Changes in Cognitive Functioning in Individuals With Psychotic Disorders. Findings From the Suffolk County Mental Health Project. JAMA Psychiatry. doi.org/10.1001/jamapsychiatry.2019.3993.