Researchers have found through a combination of animal and human research that Gene Therapy could be used to treat mental illnesses such as depression.

Depression is caused by the scarcity of a key protein according to scientist’s research published in the October 20 edition of Science Translational Medicine. Depressed people have a below normal level of a brain protein called p11.

The researchers sought to cure mice who had no p11 and were bred to have depressive symptoms such as listlessness. The p11 gene was added back with gene therapy, cells in the region began producing p11 protein, and the mice no longer displayed higher signs of despair.

“We believe that low levels of p11 may be one of the causes of depression in at least some patients,” said study leader, Michael Kaplitt an associate professor and vice chairman for research of neurological surgery at Weill Cornell Medical College, New York. “If we can restore it to normal levels, we can potentially reverse the process,” Kaplitt added.

The main function of p11 was uncovered in 2006 by Nobel Prize winner Dr. Paul Greengard of Rockefeller University. At that time, p11 was identified as a key player in facilitating the binding of the neurotransmitter serotonin -- long cited as a mood, appetite and sleep regulator -- to nerve cells.

The therapy is currently being tested on monkeys, and if it's successful, the researchers will seek approval to test it in humans within the next two years. "We potentially have a novel therapy to target what we now believe is one root cause of human depression," study author Michael Kaplitt said in a statement to reporters.

Autopsy results on human patients who had been diagnosed with severe depression revealed significantly lower amounts of the p11 gene in their brain than typically found in patients with no signs of depression, the study noted.

"Together, these studies provide strong evidence that maintaining adequate levels of this particular protein, p11, in this pleasure-reward area of the brain may be central to preventing or treating depression," Kaplitt concluded.