Neuroimaging insights into the link between depression and Insomnia: A systematic review

Abstract

Background: Insomnia is a symptom of Major Depressive Disorder (MDD) and genome wide association studies pointed to their strong genetic association. Although the prevalence of insomnia symptoms in MDD is noticeable and evidence supports their strong bidirectional association, the number of available neuroimaging findings on patients with MDD with insomnia symptoms is limited. However, such neuroimaging studies could verily improve our understanding of their shared pathophysiology and advance corresponding theories. Methods: Based on the preferred reporting items for systematic reviews and meta-analysis guideline, we have conducted a literature search using PubMed, EMBASE, and Scopus databases and systematically explored 640 studies using various neuroimaging modalities in MDD patients with different degrees of insomnia symptoms. Results: Despite inconsistencies, current findings from eight studies suggested structural and functional disturbances in several brain regions including the amygdala, prefrontal cortex and anterior cingulate cortex and insula. The aberrant functional connectivity within and between the main hubs of the salience and default mode networks could potentially yield new insights into the link between MDD and insomnia, which needs further assessment. Limitations: The number of studies reviewed herein is limited. The applied methods for assessing structural and functional neural mechanisms of insomnia and depression were variable. Conclusion: Neuroimaging methods demonstrated the overlapping underlying neural mechanisms between MDD and insomnia. Future studies may facilitate better understanding of the uniqueness of each condition to allow development of specific treatment.

Affect and Arousal in Insomnia: Through a Lens of Neuroimaging Studies

“…The amygdala plays a crucial role in processing and memorizing arousing and fear-inducing stimuli [ 30 , 31 ]. Moreover, it is discussed as an important link between insomnia and depression [ 8 •]. Given these facts, the region might be of particular interest in insomnia from a HT perspective.…”

“…Moreover, demographic trends in these countries suggest that the societal relevance of insomnia might even increase in the future [ 4 ], given the fact that the prevalence rises with age [ 2 , 5 ]. Insomnia is also closely linked to depression, as epidemiological (insomnia as a predictor of depression, see [ 6 , 7 ]) and neurobiological (for a systematic review, see [ 8 •]) research suggests. It seems therefore particularly important to understand underlying features of insomnia related to mood and affect.…”

Functional connectome fingerprint of sleep quality in insomnia patients: Individualized out-of-sample prediction using machine learning

“…We observed that the pre-frontal areas, entorhinal cortex, parahippocampal gyrus, temporal gyrus, and thalamus contributed to PSQI prediction in both groups. These regions have been consistently found to be abnormal in insomnia patients compared to controls ( O'Byrne et al, 2014 , Zhou et al, 2017 , Wang et al, 2018 , Yan et al, 2018 , Bagherzadeh-Azbari et al, 2019 ). The entorhinal cortex, parahippocampal gyrus, and temporal gyrus may play a crucial role in long-term memory encoding ( Schon et al, 2016 , Newmark et al, 2013 , Park et al, 2011 ), while the pre-frontal area is critical for working memory ( D'Esposito and Postle, 2015 ) and the thalamus is related to sleep regulation ( Coulon et al, 2012 ).…”

“…For example, these patients showed lower spontaneous activity in regions of higher-order cognitive networks ( Li et al, 2016 ) and higher activity in sensory/perception-related regions ( Zhou et al, 2017 ). Considering the interaction between regions, several studies have demonstrated abnormalities in both local regional homogeneity ( Wang et al, 2016 ) and distributed functional connectivity among regions spanning the frontal, subcortical, and parietal cortex in patients with insomnia disorder ( O'Byrne et al, 2014 , Bagherzadeh-Azbari et al, 2019 ). All these studies sought to infer patterns of abnormal brain functional activity that are common across patients.…”

Sleep Disturbance Severity is Associated With Cognitive Impairment in Patients With First-episode, Treatment-naïve Major Depressive Disorders

“…Some risk factors are unmodi able, such as age, and others are potentially modi able, such as MDD severity. Though previous studies have explored the negative consequences of sleep disturbances in patients with MDD or cognitive impairment [12,22,23], it is still not known about the role, if any, of sleep disturbances play in the development of cognitive impairment in patients with MDD.…”