New research reveals a wider variety of causes (and treatments) for depression than ever before.

People who experience depression are usually more focused on treating the condition than finding its cause. But new research is beginning to shed light on both the triggers for depression and how to alleviate it.

Depression affects one in 10 Americans at some point in their lives, and the number of patients diagnosed with depression goes up by about 20 percent each year. The World Health Organization says it is the top cause of disability worldwide, and that five to seven percent of people on Earth experience a major depressive episode in a given year.

As science evolves and more people speak out about the issue, we’re finding that depression has more root causes than anyone suspected.

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A new study in the Journal of Adolescent Health recommends that doctors screen teens with a history of concussion, as they are three times more likely to suffer from depression. Researchers evaluated data from 36,000 adolescents; of them, 2.7 percent had a concussion and 3.4 percent experienced depression.

According to the Centers for Disease Control and Prevention, 1.6 to 3.8 million sports- and recreation-related concussions occur each year in the U.S. Moreover, a mild brain injury occurs every 21 seconds, so screenings are crucial.

A research team at the Hebrew University of Jerusalem found that changes in one type of brain cell, called microglia, indicate depressive symptoms brought on by exposure to chronic stress. Microglia make up about 10 percent of brain cells and represent the immune system in the brain. They are also involved in physiological processes that have nothing to do with infection or injury—such as the body’s response to stress, research has shown.

The Israeli researchers were able to demonstrate in animals that compounds which alter the function of microglia make efficient drugs. The findings were published in Molecular Psychiatry.

Raz Yirmiya, a professor at the university, said the research shows that disturbances in microglia cells play a role in causing psychopathology in general and depression in particular.

“They may be able to help people get symptom relief faster,” said Amy Morin, a therapist from Maine, who said this could be great news for people who are experiencing a loss of day-to-day function due to depression.

“Waiting four to six weeks to see if an anti-depressant is working can be fatal for people who experience suicidal ideation as part of their depression,” she added.

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Other research also indicates that immune cells outside of the brain can play a role in the development of depression.

Scientists at the Icahn School of Medicine at Mount Sinai found that rodents with high levels of the circulating pro-inflammatory immune chemical known as interleukin-6 were more vulnerable to symptoms of depression. This suggests that differences in the peripheral immune system can affect a person’s mental state.

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The December issue of the Canadian Journal of Cardiology included a report showing that people who were inactive after cardiac surgery had as much as a 40 percent greater risk of depression.

The researchers recommend that doctors screen heart patients for depression and level of physical activity to minimize symptoms. Patients should also remain as active as possible after surgery.

Research into depression treatments is also advancing rapidly.

In an article in Biological Psychiatry, Timothy Dinan and his colleagues at University College Cork in Ireland discuss the concept of psychobiotics. These are live organisms taken like probiotics to help treat psychiatric illnesses.

Dinan and his team examined a study on the benefits of B. infantis, a specific probiotic. They found that it normalized rats’ behavior and previously abnormal immune response. Some psychobiotics have anti-inflammatory effects, which is beneficial because depression and stress are exacerbated by inflammation in the body.

“We need to be careful not to reduce all depression to a purely biological level,” noted Eileen Kennedy-Moore, a psychologist and co-author of Smart Parenting for Smart Kids. “People can have marvelously healthy guts but still need to work on communicating better with their spouse, coping with their child’s tantrums, making time for friends, managing office politics, or finding meaningful and satisfying work.”

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Morin agreed that the development could be a game-changer.

“Although it sounds a little like a science fiction movie, the research on psychobiotics is showing some interesting results,” Morin said. “It could prove to open up a lot of new possible treatment options for people suffering from depression.”

Mona Shattell, a registered nurse and professor at DePaul University specializing in mental health, said that new research on genetics and psychopharmacology—called pharmacogenomics—can help doctors determine which medication works best to treat an individual patient’s depression. This would do away with the “trial and error” method currently used, which involves testing different medications that can take weeks to have an effect.

“It can’t be overstated…providers who can better target—that is, choose the right drug the first time—will improve the quality of life for persons experiencing debilitating depression,” she said, adding that it could also have a positive impact on those experiencing despair and suicidal thoughts.

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