Depressed individuals with persistent cognitive difficulties tend to reported significantly higher levels of depression and functional impairment, according to new research published in Psychological Medicine. The findings suggest that cognitive difficulties may serve as a key indicator for targeted treatment.
Study co-authors Faith Matcham of the University of Sussex and Sara Simblett of King’s College London spoke to PsyPost about their new research.
“As a clinical psychologist specializing in neuropsychology, persistence of cognitive difficulties for people with a diagnosis of major depression is something I know to be important but challenging to measure,” explained Simblett. “It needs frequent assessments which can often be difficult to collect within a clinic setting when resources are limited.
The researchers analyzed data collected by a prospective observational cohort study known as the Remote Assessment of Disease and Relapse – Major Depressive Disorder (RADAR-MDD).
“When the RADAR-MDD study was being designed and set-up (by Dr Matcham), integrating a regular and objective assessment of cognitive function was a priority and we were excited about the opportunity it would bring to investigate this clinically important experience,” the researchers explained.
The study included 623 individuals with recurrent MDD, which is characterized by repeated episodes of depression. Each participants was provided with a specialized smartphone app to use, which delivered questionnaires regarding subjective cognitive difficulties along with objective tests of cognitive performance every 6 weeks.
These smartphone-based assessments were collected alongside assessments of depression and functioning every 3 months. The study lasted for a minimum of 11 months and a maximum of 24 months, and the median duration was 541 days. For the current study, the researchers examined a subset of 448 participants who had provided sufficient data.
The researchers were particularly interested in the persistence of cognitive difficulty — in other words, those who repeatedly had below average scores across multiple timepoints. They found that both persistent self-reported cognitive difficulties and objectively-measured problems with attention, working memory, processing speed, and executive function were associated with higher levels of depression and functional impairment.
“People who have been diagnosed with major depression who currently have persistent cognitive difficulties have higher levels of long-term depression severity and functional impairment (e.g., difficulties returning to work or to leisure activities) than people who do not have these problems with persistent cognitive difficulties,” Matcham and Simblett told PsyPost.
“Persistent cognitive difficulties should be a target for future treatment development, as working with this aspect of the condition has the potential to reduce future depression severity and improve functional outcomes.”
When examining cognitive domains individually, the researchers found that impaired attention was particularly associated with worse work and private-leisure functioning, while impaired working memory reported was particularly associated with worse functioning related to private leisure, social leisure, work, and relationships over time.
Persistent problems with processing speed and executive function, meanwhile, were negatively associated with worse functioning related to private leisure, social leisure, work, relationships, and household activities.
Interestingly, the researchers identified substantially more people with persistent objectively-measured cognitive difficulties than persistent self-reported cognitive difficulties.
“We were interested to find that the people in our sample under-reported their own cognitive difficulties in that the self-report questionnaires showed lower levels of difficulties than the objective tests,” the researchers said. “This highlights why healthcare services for people with Major Depression may need to incorporate neuropsychological assessment with tests designed to pick up cognitive difficulties.”
However, future research is needed to understand the direction of the relationships and explore interventions that target both cognitive and functional disability.
“Our analyses are not causal; we cannot state that persistent cognitive difficulties cause more severe depression or difficulties in daily functioning,” Matcham and Simblett said. “But there is a clear relationship between these factors.”
“We would like to thank the RADAR-CNS consortium and the Patient Advisory Board for supporting this work,” they added.
The study, “The association between persistent cognitive difficulties and depression and functional outcomes in people with major depressive disorder“, was authored by F. Matcham, S. K. Simblett, D. Leightley, M. Dalby, S. Siddi, J. M. Haro, F. Lamers, B. W. H. J. Penninx, S. Bruce, R. Nica, S. Zormpas, G. Gilpin, K. M. White, C. Oetzmann, P. Annas, J. C. Brasen, V. A. Narayan, M. Hotopf, T. Wykes, and for the RADAR-CNS consortium