In a recent study published in JAMA Network Open, researchers aimed to identify and understand a subgroup of individuals with Major Depressive Disorder (MDD) characterized by cognitive impairment. Specifically, they aimed to confirm the existence of a cognitive dyscontrol biotype by examining its symptom and function profiles, investigating neural dysfunctions, assessing its response to antidepressant treatment, and exploring the role of cognitive impairment in treatment outcomes.
MDD is a debilitating condition that affects millions of people worldwide. It is characterized by persistent feelings of sadness, hopelessness, and a loss of interest or pleasure in most activities. While depression is typically associated with emotional symptoms, cognitive impairments are increasingly recognized as a significant part of the disorder. These cognitive deficits can include difficulties with memory, attention, decision-making, and executive function, which encompasses the ability to plan, organize, and manage tasks.
Researchers have been studying cognitive impairments in depression for some time, but previous studies often lacked consistency in the way cognitive measures were assessed. This lack of standardized assessment methods made it challenging to pinpoint specific cognitive deficits in individuals with MDD. Additionally, there was a need to explore whether certain subgroups of individuals with MDD exhibited more pronounced cognitive impairments.
“One of the big challenges is to find a new way to address what is currently a trial-and-error process so that more people can get better sooner,” said the study’s senior author, Leanne Williams of Stanford Medicine. “Bringing in these objective cognitive measures like imaging will make sure we’re not using the same treatment on every patient.”
The study involved 1,008 adults diagnosed with MDD who participated in the International Study to Predict Optimized Treatment in Depression. For functional and structural neuroimaging, data from a subset of 96 individuals was analyzed. This imaging helped identify brain regions associated with cognitive control.
The researchers collected data through cognitive testing, symptom assessments, functional capacity evaluations, and functional neuroimaging at baseline. The participants were then randomized to receive one of three commonly prescribed antidepressants (escitalopram, sertraline, or venlafaxine-XR) and reassessed after eight weeks of treatment.
Using a machine learning method of cluster analysis, the researchers identified a subgroup of MDD patients characterized by significant cognitive impairment. This cognitive biotype was associated with greater baseline symptom severity (e.g., insomnia, slower information processing) and functional impairment compared to other MDD patients.
Moreover, this cognitive biotype demonstrated reduced neural activation in key brain regions, specifically the right dorsolateral prefrontal cortex (dLPFC) and dorsal anterior cingulate (dACC), which are integral to cognitive control. Furthermore, the biotype with cognitive impairment had a notably lower response and remission rate to antidepressant treatment.
While unidentified behavioral or neurobiological factors may still play a role in the cognitive biotype, these findings emphasize the critical need to unravel the heterogeneity within depression. Furthermore, they highlight that this biotype is characterized more by specific individual symptoms rather than overall depression severity.
This underscores the significance of cognitive impairment as a major contributor to disability in depression. Consequently, these results stress the urgency of developing treatments that specifically target cognitive impairment and its underlying mechanisms in the context of depression.
“This study is crucial because psychiatrists have few measurement tools for depression to help make treatment decisions,” said Laura Hack, the lead author of the study and an assistant professor of psychiatry and behavioral sciences. “It’s mostly making observations and self-report measures. Imaging while performing cognitive tasks is rather novel in depression treatment studies.”
The study, “A Cognitive Biotype of Depression and Symptoms, Behavior Measures, Neural Circuits, and Differential Treatment Outcomes: A Prespecified Secondary Analysis of a Randomized Clinical Trial“, was authored by Laura M. Hack, Leonardo Tozzi, Samantha Zenteno, Alisa M. Olmsted, Rachel Hilton, Jenna Jubeir, Mayuresh S. Korgaonkar,Alan F. Schatzberg, Jerome A. Yesavage, Ruth O’Hara, and Leanne M. Williams.