An estimated 350 million people around the world, and 3.3 million American adults, suffer from depression.
In the U.S., 10 percent of adults (and as many as 25 percent of women in their 40s and 50s), are taking antidepressants, most of which operate by targeting serotonin receptors in the brain. While we know that serotonin -- a brain chemical involved in the regulation of mood, sleep, sexual desire and social behavior -- likely plays a role in mood disorders like anxiety and depression, we understand startlingly little about how it works.
The most commonly-prescribed antidepressants, selective serotonin reuptake inhibitors (SSRIs), target neurotransmitters, preventing the reabsorption of serotonin. This changes the balance of serotonin, helping brain cells to send and receive messages, and in turn boosts mood. While SSRIs can help boost mood for many users, they can also have serious side effects, including nausea, sexual disfunction and insomnia. More troublingly, antidepressants are only estimated to be effective for roughly half of the patients who take them.
To better understand the workings of serotonin, scientists at Johns Hopkins Brain Science Institute are seeking to create a "serotonin map of the brain" with the hope of improving the efficacy of antidepressants and reducing common side effects, The Guardian reported.
Currently, most antidepressants operate broadly on the serotonin across the brain, rather than targeting the chemical in specific brain areas associated with mood and various emotions. According to the project's leader, Dr. Jeremiah Cohen, these pharmaceuticals are limited by our lack of knowledge about the workings of serotonin.
"We are working with a blunt system and we need to refine it," Cohen told The Guardian.
Cohen's research will begin by studying serotonin neurons in mice while they are performing reward-and-punishment tasks. The researchers will monitor the mice's behavior during the tasks, and map the neurons that are participating in responses that give rise to the behavior.
"The ultimate aim is to understand the biology of mood and how groups of cells in the brain connect to produce our emotional behavior," Cohen said. "What we hope to do with this map is use drugs that are available or design new drugs that will target only the components of that system relevant to a particular disorder."