Long-Standing Belief about Depression Called into Question: Is it All Serotonin?

Scientists may have new evidence that calls a long-standing belief about depression into question. A new study reveals that mice lacking the ability to make serotonin, a chemical, in their brains did not show depression-like symptoms.

Depression is a major public health concern. In fact, more than 350 million people suffer from the condition, according to the World Health Organization. It's also the leading cause of disability across the globe. In the past, researchers have long believed that a deficiency in serotonin plays a central role in depression. That's why the well-known antidepressant, Prozac, works by increasing the amounts of serotonin in the brain.

Yet Prozac doesn't solve everyone's depression. In fact, researchers now know that 60 to 70 percent of patients continue to feel depressed, even while taking drugs. That's why scientists wanted to see the role that serotonin played in the condition.

In order to find out, the researchers created "knockout" mice that lacked the ability to produce serotonin in their brains. Then, the scientists ran a series of behavioral tests to see if they would show signs of depression.

So what did they find? While the mice were compulsive and aggressive, they didn't show signs of depression-like symptoms. When the mice were put under stress, though, they behaved in the same way most of the normal mice did. This suggests that serotonin is not a major player in depression and that different factors must be involved.

The findings reveal that further research is needed when it comes to depression. More specifically, scientists should look at other avenues of treatment besides just focusing on serotonin. This could eventually help create better drugs and treatments for patients in the future.

The findings are published in the journal Chemical Neuroscience.