Depressed people are often withdrawn and antisocial. This doesn't necessarily mean that they don't like other people, but it could mean that their brains don't process feelings of hate in a normal way, a new study suggests.
Scientists in China and the UK scanned the brains of people with and without depression, and they found a surprising pattern in nearly all of the depressed people: Their brain activity was out of sync in three regions collectively known as the "hate circuit"-- so called because in previous experiments they have been shown to light up when people look at photographs of someone they can't stand.
"We were a bit shocked when we first saw these results," says lead researcher Jianfeng Feng, a professor of computer science at the University of Warwick who specializes in biology. Feelings of self-hatred are a common feature of depression, he explains, so one would expect those feelings to also be more intense when directed toward other people.
Instead, it's as if the brains of depressed people hate incorrectly. The brain disruptions the researchers observed could be a sign that people with depression have an impaired ability to cope with -- and learn from -- social situations in which they feel hate, Feng says. This may explain why they often turn emotions such as hatred and anger inward, instead of handling them in more constructive ways, he adds.
The study, which was published today in the journal Molecular Psychiatry, is the first to connect disruptions in the hate circuit to depression, and the findings may help doctors understand why depressed people react the way they do to certain circumstances, says Madhkar Trivedi, M.D., director of the mood disorders program and clinic at the University of Texas Southwestern Medical Center at Dallas.
"These patients start doubting themselves and they withdraw from social situations," says Trivedi, who was not involved in the study. "The hate circuit might have something to do with that."
Discoveries like this warrant a good deal of interest, Trivedi says, though he cautions that the results are preliminary. "It is exciting when something is this novel and this promising, but ... I would of course like to see some results replicated by other researchers," he says.
Feng and his colleagues used functional magnetic resonance imaging (fMRI) to scan the brains of 37 healthy people and 39 people who had received a depression diagnosis but had not sought treatment or responded to antidepressant medication. The makeup of each group was similar in terms of age, sex, and education levels.
In a healthy brain, the waves recorded by fMRI move up and down together in a continuous pattern. But when brain function is disturbed, the waves move out sync with each other -- a phenomenon known as “uncoupling.”
The brain waves in the hate circuit were uncoupled in 92 percent of the depressed patients, the researchers found. Depression was also associated with disruptions in parts of the brain involved in action and risk-taking, emotion and reward-seeking, and attention and memory processing.
Most MRI research in depressed people has treated the brain as a group of discrete regions, by targeting very specific areas or by looking at how regions behave independently. This study, by contrast, observed the entire brain system at once -- an approach that helped the researchers spot connections and patterns across multiple regions.
Feng and his colleagues performed the scans while the subjects were resting. This minimized interference from any outside stimuli, but it also means the researchers can't be sure if the brain disruptions they observed are likely to carry over into active settings, such as social situations.
Further research will be needed to confirm and extend his team's findings, Feng says. In the future, he says, a focus on the hate circuit may open new avenues for treatment -- including new drugs and psychotherapies -- that target this and other specific circuits in the brain.
"We might have to think about depression from more wide angles," he says.