Does objectively-assessed sleep moderate the association between history of major depressive disorder and...

Executive function and psychomotor speed are consistently impaired in patients with major depressive disorder (MDD). Persistent cognitive impairments after depression remission are thought to reflect "scarring" from the neurotoxic effects of hypothalamic-pituitary-adrenal axis activity during a depressive episode. As sleep also deteriorates with depression and restores daytime executive functions, we examined whether adequate sleep could be protective against task-switching and psychomotor impairments associated with a history of MDD.

This cross-sectional study tested task-switching associations with MDD history, sleep, and their interaction to determine whether sleep continuity and sleep duration moderate the relationship between MDD history and task-switching performance.

After adjusting for age, sex, education, current depressive symptoms, and use of anti-depressants, a history of MDD, particularly recurrent MDD, was associated with slower response speed and disproportionately lower accuracy on repetition trials compared to switch trials, reflecting impaired adoption of a task-set. Regardless of MDD history, higher wake after sleep onset and shorter total sleep time were associated with slower response times, but neither sleep measure moderated the association between depression history and task-switching performance.

This cross-sectional study cannot assess the causal direction of associations. One night of sleep in the laboratory was used to assess sleep and a single task-switching paradigm was used to assess executive function.

These results suggest that longer, more continuous sleep is associated with greater psychomotor speed across healthy controls and those with a history of MDD, but MDD-task-switching associations are not mitigated by longer or more continuous sleep.