Depression is characterised by an overarching, persistent low mood. A great deal of research into the treatment of depression has therefore predominantly focused on understanding and elevating this debilitating symptom. However, it may be surprising to some that this disorder actually encompasses a constellation of symptoms relating to appetite, sleep, cognitive functions and self-esteem. Researchers from the Department of Psychiatry at the University of Cambridge set out to highlight the complexity of depression in an editorial published earlier this year in Psychological Medicine. Specifically, the authors argued for the importance of impaired cognitive function and the need for effective treatment of this symptom, which is largely overlooked in both clinical and research settings.
Cognitive functions are mental processes such as reasoning, perception, memory and concentration. Importantly, these are distinct from the “cognitions” targeted in Cognitive-Behavioural Therapy (CBT), which refer to negative emotional thoughts about our self-perception and feelings. It has been estimated that 90% of patients with depression suffer with cognitive impairments, such as deficits in memory and concentration, yet few treatment studies include assessment of cognitive functioning.
“A major problem in the literature is that most of the treatment studies (pharmacological or psychological) do not include cognitive outcomes. Therefore, our understanding of which treatments can improve cognition in depression is limited. From the research point of view, cognitive assessment should be a part of treatment studies. This will allow us to understand which interventions can improve cognition in depression and will give rise to novel treatments which may help improving cognition,” said lead author, Dr Muzaffer Kaser.
Sufficient cognitive functioning is imperative for the majority of everyday activities, from remembering to pick up the weekly food shop to meeting important deadlines in work. Consequently, impairment in these processes can have a significant impact on quality of life. Deficits in memory and concentration have been linked to unemployment and poorer work performance. Despite this, pharmacological and psychological treatments for depression predominantly target emotion regulation. Due to the current lack of investigation into cognition, it is unclear whether these treatments show any effect on cognition.
Professor Barbara Sahakian, senior author, added: “Depressed patients with poorer cognition have both poorer outcomes and more frequent relapse. Therefore, if we are to improve outcomes for our patients, we need to successfully treat their cognitive problems, which are not effectively treated by antidepressant drugs.”
Studies that have investigated antidepressant treatment effects on cognition in depression have struggled to demonstrate any change in these symptoms post-treatment. These deficits persist long after mood symptoms recover. However, modafinil, a drug originally used to treat narcolepsy, is receiving increasing attention for its pro-cognitive effects in depression. The current authors recently published a separate study in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging that demonstrated improved memory function following treatment with modafinil in depressed patients. This has inspired the authors to further investigate long-term outcomes of modafinil in treating cognitive dysfunction in depression. The article on this paper can be read in full here.
When discussing psychological treatments, Dr Kaser added: “A new line of psychological treatment, cognitive remediation therapy claims that it addresses cognitive dysfunction in depression. However, the number of studies is limited, and the problem of active controls groups remains to be a critical issue for psychological treatment studies.”
Overall, the editorial advocates that cognitive dysfunction should be recognised as a treatment target in depression. A heavier focus on cognition in treatment trials will advance understanding of the role of cognition in the course of depression, and, consequently, overall patient outcome will improve.
Written by Sian Emma Davies.