Understanding of the physical root of depression has taken a huge leap forward thanks to research by the University of Warwick in Coventry, England and Fudan University in Shanghai, China
Their joint study shows that depression affects the "lateral orbitofrontal cortex" or the part of the brain implicated in non-reward so that sufferers of the disease feel a sense of loss and disappointment associated with not receiving rewards.
This area of the brain, which becomes active when rewards aren't received, is also connected with the part of the brain involved in one's sense of self, thus potentially leading to thoughts of personal loss and low self-esteem.
Depression is also associated with reduced connectivity between the reward brain area in the medial orbitofrontal cortex and memory systems in the brain, which could account for sufferers having a reduced focus on happy memories.
These new discoveries could herald a breakthrough in treating depression by going to the root cause of the illness, and helping depressed people to stop focusing on negative thoughts.
The study has been carried out by Prof. Edmund Rolls from Warwick; Prof. Jianfeng Feng from Warwick and from Fudan University in Shanghai; Dr. Wei Cheng from Fudan University, and by other centers in China.
In a particularly large study, almost 1,000 people in China had their brains scanned using high precision MRI, which analyzed the connections between the medial and lateral orbitofrontal cortex -- the different parts of the human brain affected by depression.
Prof. Feng noted that depression is becoming increasingly prevalent.
"More than one in 10 people in their lifetime suffer from depression, a disease which is so common in modern society and we can even find the remains of Prozac (a depression drug) in the tap water in London," he said.
"Our finding, with the combination of big data we collected around the world and our novel methods, enables us to locate the roots of depression which should open up new avenues for better therapeutic treatments in the near future for this horrible disease."
Prof. Rolls looks forward to the new treatments the research could lead to.
"The new findings on how depression is related to different functional connectivities of the orbitofrontal cortex have implications for treatments in the light of a recent non-reward attractor theory of depression," he said.
The research, 'Medial reward and lateral non-reward orbitofrontal cortex circuits change in opposite directions in depression', was published in the neurology journal, Brain (doi: 10.1093/brain/aww255).