One of the most common and mysterious mental illnesses, depression, might have found an explanation in recent studies conducted on mice, by neuro-engineers at Stanford University.

"Depression raises all kinds of questions," Karl Deisseroth, team leader says. "It has all sorts of symptoms and responds to a variety of drugs that act in different ways." Almost 15 million people nationwide suffer from a "major depressive disorder," according to the federal National Institute of Mental Health.

Previous studies in both humans and mice indicated a highly significant relationship between a part of the brain called hippocampus and the ignition of depression. Researchers have literally sliced stressed and depressive mice’s brains and then analyzed the hippocampus. They’ve discovered that this part of the brain had suffered small-to-severe shrinkage in stressed mice, while the mice that had previously received anti-depressants like fluoxetine (also administered to humans) had a normal sized hippocampus.

Moreover, it was later discovered- through a novel electronic circuit test called "voltage-sensitive dye imaging"- that electric charges sent through the sliced brains (neuron tissue lives on for about five hours after death) simply stopped in the hippocampus at the depressed rats, while the same electric charges sent through the sliced brains of non-depressive or depressants-treated rats went straight through. 

Karl Deisseroth’s study, published in the latest issue of Science Magazine, suggests that the hippocampus could be common pathway or intersection for brain activity in those suffering from depression, humans included.

"One of the mysteries of depression is how there can be so many different causes … and so many different treatments." A common pathway would bridge them, he added.