Study reveals duration of depression may impact severity of brain changes

The duration for which one remains depressed may impact how severely the mental disorder makes changes in the brain, according to a study.
Researchers from the University of Sao Paulo in Brazil and University of Oxford in the UK analysed brain images from 46 patients with major depression.
Results suggest that the duration of depressive episodes is associated with differences in functional brain connectivity. The findings could help with developing personalised treatments.
“Major depression can alter brain function compared to people without the disorder,” first author Tamires Zanao, a Sao Paulo Research Foundation (FAPESP) fellowship recipient, University of Sao Paulo, said.
However, the study identified that chronic patients, or those with depression for more than 24 months, and non-chronic ones displayed distinct connectivity patterns between two networks- the central executive network (CEN), focused on executive control, and the default mode network (DMN), associated with introspective thoughts and self-reflection, Zanao said.
“The key finding was that chronicity moderated the impact of severity on functional connectivity between the Central Executive Network (CEN) and the precuneus (part of the Default Mode Network, DMN),” the authors wrote. While typically, both the networks exhibit dynamics in coordination with the salience network- involved in switching focus between the external environment and internal processes- in depression, the dynamics may be altered, associated with symptoms such as rumination and difficulty concentrating, the researchers said.
“That misalignment between those networks may favour the predominance of introspective and self-referential thoughts, often with a negative bias. That helps explain why people with depression tend to get stuck in negative thoughts and have difficulty directing their attention to the environment when necessary,” Zanao explained.
Brain regions that help with executive control required for goal-oriented tasks include the dorsolateral prefrontal cortex, while those involved with internal processes such as self-reflection and spontaneous thoughts are the medial prefrontal cortex, precuneus, and hippocampus.
The default mode network divided into subnetworks, such as those involving the precuneus which serves as a central hub for brain connectivity.
The researchers found that the duration of depression appears to be associated with the dynamics of the central executive network and default mode network. Among those with more recent episodes, the functional link between the CEN and precuneal regions in the DMN decreases as symptoms worsen.
“The results are consistent with the hypothesis that changes in brain connectivity in depression may evolve over time. (PTI)