Abstract
BackgroundAdequate and timely identification of depression is essential to improve patient care. A potential method to achieve this is by using neuroimaging. Many neuroimaging studies have revealed widespread abnormalities in brain structure and function in patients with depression, but in most studies only single neuroimaging modalities were used. Links between abnormalities in brain structure and function need to be therefore further explored in order to define diagnostic and therapeutic applications.MethodsA systematic literature review according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines was conducted.ResultsOut of 2,516 articles, only 14 studies were eligible to be included. These studies combined structural and functional neuroimaging methods in depressed patients compared to controls. Four studies reported a negative relationship between brain structure and function within the default mode network: reduced gray or white matter integrity in depressed patients compared to healthy controls was associated with enhanced neural activity or connectivity. The other studies reported positive relationships (two studies), mixed relationships (two studies), or no link (six studies) between structural and functional brain abnormalities.ConclusionThis systematic literature review revealed no robust relationship between abnormalities in brain structure and function in patients with depression. Remarkably, only 14 studies could be included and four of these suggested enhanced default mode network connectivity associated with reduced structural brain integrity. In the ongoing development of the diagnostic and treatment applications of neuroimaging, large-scale studies that combine structural with functional neuroimaging are required to determine the relationship between structural and functional abnormalities in depression.
Highlights
Depression is the second leading cause of disability worldwide and one of the most prevalent psychiatric disorders [1]
These results suggest that activity is increased within networks that are important for directing attention to the internal world (DMN), whereas activity is reduced within brain networks that are important for directing attention to the outside world (SN) and performing goal-directed actions (CEN)
Another study included in this review focused on the subgenual anterior cingulate cortex (ACC) by investigating its volume and activity during an “N-back” working memory task [31] in depressed patients compared to controls
Summary
Depression is the second leading cause of disability worldwide and one of the most prevalent psychiatric disorders [1]. A broader understanding of underlying pathophysiology of depression is fundamental to detect (and hopefully to prevent) this condition in an early stage and to further distinguish phenotypes within this heterogeneous clinical syndrome. Various neuroimaging methods have been used to explore distinct underlying neural mechanisms of depression. These have been based on several proposed neurobiological models and are mostly aimed to localize specific structural and functional abnormalities. Many neuroimaging studies have revealed widespread abnormalities in brain structure and function in patients with depression, but in most studies only single neuroimaging modalities were used. Links between abnormalities in brain structure and function need to be further explored in order to define diagnostic and therapeutic applications
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