Cognitive models of depression have proposed that depressed individuals may struggle to pull attention from negative information, selectively focusing on distressing elements of experience, and subsequently, increasing negative thoughts. Most scholars agree that the ability to regulate where our attention goes and what information it retains, otherwise known as cognitive control, is made up of three separate but related executive functions. These include 1) inhibition: the ability to resist distraction from task-irrelevant information; 2) updating of working memory: the ability to flexibly add and remove items from short-term memory according to relevance to the task; and 3) set shifting: the ability to switch between different sets of information as task demands change. Studies on cognitive control in depression have found that when depressed individuals are working through tasks that involve emotional information, they have more difficulty exerting cognitive control than their non-depressed counterparts.
The relationship between depression and impaired inhibition is well-documented, with depressed individuals showing difficulty disengaging from negative information. Studies assessing working memory and set-shifting in depression have yielded mixed results and are more limited. Additionally, few studies have assessed whether there is a general impairment in executive functioning, as opposed to specific impairments in the three aforementioned abilities. There is preliminary evidence that depressed individuals struggle to discard negative information from working memory even after their depression has remitted, which could suggest that negatively-biased working memory is a stable trait of people who tend to develop depression, rather than an aspect of the depressed mood itself. Studies assessing the other executive functions in remitted depression are limited.
In the study “Cognitive control over emotional information in current and remitted depression,” Quigley et al. assessed the executive functions of inhibition, working memory and set shifting in both current and remitted depression, with the ultimate aim of identifying which domains of executive functioning are impacted in depression, and to what extent this impairment is a stable trait of people who tend get depressed.
In line with the researchers’ hypothesis, currently depressed participants showed difficulty exerting cognitive control when working with emotional information. This included depressed individuals being more easily distracted by negative information, though not neutral or positive information, showing impaired ability to regulate emotional information stored in working memory, and being slower to shift from a task involving emotional information to a neutral task. In the latter two domains, working memory updating and set shifting, depressed participants showed impaired performance regardless of whether the information they were working with was emotional or not. Participants with remitted depression did not show similar impairments.
These results provide further evidence for impaired and biased cognitive control in those with depression, particularly in the specific domains of working memory updating and set shifting, for which prior evidence was limited.