People with depression have increased connections among most of their brain areas, scientists have proven for the first time.
While it has been commonly accepted that depression is a result of a malfunction involving brain networks, the exact nature of these has not been known.
Symptoms associated with depression – anxiety, poor attention and concentration, memory issues, and sleep disturbances – originate in different areas of the brain, and the sheer volume of symptoms led scientists to believe it is a fault with communication within the brain, rather than a single region.
A team from the University of California Los Angeles (UCLA) has now identified for the first time that depressed people have in fact got increased connections among most areas of the brain; their brains are essentially hyperconnected.
Dr Andrew Leuchter, a professor of psychiatry at the Semel Institute for Neuroscience and Human Behaviour at UCLA, said the inability of patients with depression to control these connections could be the cause of some depressive symptoms.
"The brain must be able to regulate its connections to function properly. The brain must be able to first synchronize, and then later desynchronize, different areas in order to react, regulate mood, learn and solve problems," he explained.
The researchers studied the connections in the brain of 121 adults diagnosed with major depressive disorder, or MDD.
Using a system called weighted network analysis, they examined the overall brain connections. The subjects showed increased synchronization across all frequencies of electrical activity suggesting dysfunction in a number of different brain networks, including some involved in the release of serotonin and other chemicals which control mood.
Dr Leuchter said: "The area of the brain that showed the greatest degree of abnormal connections was the prefrontal cortex, which is heavily involved in regulating mood and solving problems.
"When brain systems lose their flexibility in controlling connections, they may not be able to adapt to change."
The next step in the research is establishing to what extent antidepressants normalise these connections.