An increase in functional connectivity in certain regions of the brains of people with depression could explain the link between the disease and poor sleep quality – and could have implications for the treatment of both conditions, the first research of its kind suggests.
Wei Cheng, PhD, of the Institute of Science and Technology for Brain-Inspired Intelligence at the Fudan University in Shanghai, China, and colleagues noted that many people with depression report poor sleep quality and sleep disturbance.
“Understanding the neural connectivity that underlies both conditions and mediates the association between them is likely to lead to better-directed treatments for depression and associated sleep problems,” they wrote in JAMA Psychiatry.
In the current study, the research team used data from 1,017 participants of the Human Connectome Project drawn from the general population in the United States (who were not selected for symptoms of depression). Subjects, whose ages ranged from 22 to 35 years, had completed the Adult Self-Report of Depressive Problems portion of the Achenbach Adult Self-Report for Ages 18-59 – a survey of self-reported sleep quality and resting-state functional MRI.
“Resting-state functional connectivity between brain areas, which reflects correlations of activity, is a fundamental tool in augmenting understanding of the brain regions with altered connectivity and function in mental disorders,” the study authors noted.
The researchers then cross-validated the sleep findings using a sample of 8,718 participants from with the United Kingdom Biobank data set.
In total, the research team identified 162 functional connectivity links involving areas associated with sleep, with 39 of these areas also associated with Depressive Problems Scores (P less than .001).
Overall, the brain areas with increased functional connectivity associated with the Pittsburgh Sleep Quality Index score and Depressive Problems scores included the lateral orbitofrontal cortex, dorsolateral prefrontal cortex, anterior and posterior cingulate cortices, insula, parahippocampal gyrus, hippocampus, amygdala, temporal cortex, and precuneus.
A mediation analysis conducted by the authors aimed at assessing the underlying mechanisms showed that “these functional connectivities underlie the association of depressive problems score with poor sleep quality (P less than .001).”
They observed “much smaller” associations in the reverse direction – in that the associations of sleep quality with depressive problems mediated by these links were less significant.
“ and this in turn has implications for treatment because of the brain areas identified,” the research team concluded.
Dr. Cheng and colleagues cited several limitations. One is that the Depressive Problems scores used were not reflective of a formal diagnosis. Nevertheless, they said, the current findings provided “strong support” for the role of the lateral orbitofrontal cortex in depression, particularly as the investigators observed relatively high correlations with functional connectivities in this area of the brains of 92 participants who had been diagnosed with a major depressive episode over their lifetime.
“The understanding that we developed in this study is consistent with areas of the brain involved in short-term memory (the dorsolateral prefrontal cortex), the self (precuneus), and negative emotion (the lateral orbitofrontal cortex) being highly connected in depression which results in increased ruminating thoughts that are at least part of the mechanism that impairs sleep quality,” they added.
The study was supported by several entities, including the Shanghai Science & Technology Innovation Plan and the National Natural Science Foundation of China. No conflicts of interest were reported.
SOURCE: Cheng W et al. JAMA Psychiatry. 2018 Jul 25. doi: 10.1001/jamapsychiatry.2018.1941.