Battling clinical depression is difficult, and because different medications affect people differently, some of those diagnosed can't turn to them for help. But there could be new hope; scientists say the discovery of a new pathway in the brain may be used to treat the common mental illness.

For a study published Oct. 4 in Molecular Psychiatry, those scientists from Northwestern University were looking to better understand how different kinds of antidepressants work and found that they target a pathway in the brain’s hippocampus — the center for memory and the signaling of involuntary body functions like breathing and heartbeats — known as the BMP signaling pathway. Northwestern reported that the group found the drug Prozac and tricyclic antidepressants “inhibit this pathway and, thereby, trigger stem cells in the brain to produce more neurons … involved in mood and memory formation.”

The scientists then used mice to test a brain protein called Noggin that is known to block that same pathway and cause new neurons to form.

“We hypothesized it would have an antidepressant effect, but we weren’t sure,” Sarah Brooker, the first study author and a medical student at Northwestern, said in a statement from Northwestern. But the protein had exactly that effect in mice. According to the university, “They discovered Noggin blocks the pathway more precisely and effectively than Prozac or tricyclics.”

Depressed mice that are held by the tail tend to hang hopelessly, the university explained, but with the Noggin the mice tried “energetically” to get upright. Mice treated with Noggin also appeared less anxious in exploring mazes.

“Our findings may not only help to understand the causes of depression, but also may provide a new biochemical target for developing more effective therapies,” senior study author and neurologist Dr. Jack Kessler said in the statement from the university.

Depression affects millions of people in the United States. Statistics show that between 3 and 5 percent of adults suffer from major depression, which is characterized by the person feeling “discouraged, sad, hopeless, unmotivated, or disinterested in life in general” for an extended period of time, according to international nonprofit organization Anxiety and Depression Association of America.

Source: Brooker SM, Gobeske KT, Chen J, Peng C-Y, Kessler JA. Hippocampal bone morphogenetic protein signaling mediates behavioral effects of antidepressant treatment. Molecular Psychiatry. 2016.