Researchers found subjects who had experienced multiple episodes of depression showed disruption to the brain's emotional networks.
Study coauthor Scott Langenecker, associate professor of psychiatry and psychology at the University of Illinois at Chicago (UIC), and colleagues publish their findings in the journal Psychological Medicine.
Major depression is one of the most common mental disorders experienced by Americans, affecting around 14.8 million adults in the US in any given year.
Increasingly, researchers are finding out more about how depression relates to interference with specific connections in the brain, with a view to informing better treatment strategies.
Previous research has revealed that in depression, and numerous other mental disorders, there is disruption to brain networks that work simultaneously during emotional processing and problem-solving.
On the other hand, some studies have suggested that in the "resting network" of the brain - parts of the brain that are active during rest or self-reflection - hyperconnectivity, or excessive connections between brain cells, is tied to depression.
"If we can identify different network connectivity patterns that are associated with depression, then we may be able to determine which are risk factors for poorer outcomes down the line, such as having multiple episodes, and we can keep those patients on preventive or maintenance medication," notes Langenecker.
Additionally, he adds that such information would enable health professionals to determine what treatment is best for depression patients based on their individual patterns of brain connectivity, which would pave the way for more personalized treatments.
Comparing brain effects of single and multiple depressive episodes
Previous research from the team, conducted in young adults with depression, identified hyperconnectivity in the emotional and cognitive brain networks, while another study in adolescents with a history of depression revealed hyperconnectivity in the brain areas linked to rumination - continuously thinking about the same subject.
In this latest research, Langenecker and colleagues set out to determine whether brain connectivity patterns differ between young adults who have only experienced one depressive episode and those who have experienced multiple episodes.
According to Langenecker, around half of people who have one episode of depression go on to experience another within 2 years, so identifying different brain connectivity patterns between single and multiple episodes could help determine which patients will benefit from antidepressant treatment to prevent recurrence.
To reach their findings, the researchers scanned the brains of 77 adults - with an average age of 21 - using functional magnetic resonance imaging (fMRI). All brain scans were conducted when the subjects were in a resting state, allowing the team to identify which brain areas are most synchronously active when a person is relaxed.
Of the subject studied, 17 had major depression at the time of the brain scan, 34 had a history of major depression and 26 had never experienced depression. The researchers assessed how many depressive episodes those with current depression or a history of the condition had experienced.
Multiple depressive episodes may disrupt emotional processing
Compared with controls and subjects who had experienced one depressive episode, those who had experienced multiple episodes of depression showed a "decoupling" between the amygdala - a brain region that plays a role in detecting emotion - and the emotional network, which the researchers say could disrupt the accuracy of emotional-information processing.
This finding, says Langenecker, may explain why many people with depression often perceive information to be negative, even information that is neutral - a concept known as "information-processing bias."
Furthermore, the team found that subjects who had experienced at least one episode of depression - regardless of whether they were depressed at the time of fMRI - showed increased connectivity between the resting network and cognitive network of the brain.
"This may be an adaptation the brain makes to help regulate emotional biases or rumination," says Langenecker.
While this research helps shed light on the brain activity of individuals with depression, Langenecker says much more research is warranted:
"Since this study provides just a snapshot of the brain at one point in time, longer-term studies are needed, to determine whether the patterns we saw may be predictive of a future of multiple episodes for some patients and might help us identify who should have maintenance treatments and targets for new preventive treatments."
Medical News Today recently reported on a study that suggests brain scans could predict which children are at high risk for later-life depression.