Researchers have identified a region of the brain that functions abnormally in people with depression, according to a new study published in the journal Molecular Psychiatry.
The researchers (from University College London) found that the habenula, a pea-sized group of nerve cells which responds to bad experiences, has the opposite reaction to expectations of aversive events in people with depression compared to healthy adults.
During the study, 50 volunteers were given MRI scans; 25 people with depression and 25 people without. The participants were shown a sequence of abstract pictures while they lay inside the scanner. They were told that different pictures were associated with either positive or negative outcomes. Images that preceded electric shocks were found to cause increased habenula activity in healthy volunteers, but decreased activity in those who were depressed.
The researchers also found that people with smaller habenulae are more likely to have symptoms of anhedonia, a lack of interest or pleasure in life.
The study’s senior author, Professor Jonathan Roiser, said: ‘A prominent theory has suggested that a hyperactive habenula drives symptoms in people with depression: we set out to test that hypothesis.’
‘Surprisingly, we saw the exact opposite of what we predicted. In people with depression, habenula activity actually decreased when they thought they would get a shock. This shows that in depressed people the habenula reacts in a fundamentally different way. Although we still don’t know how or why this happens, it’s clear that the theory needs a rethink.’
This is a fascinating study for those with an interest in the scientific basis of depression and may well lead to changes in widely held views of it origins and effects. Unfortunately at this stage it doesn’t promise any clinical application, because as the senior author says, we still don’t know how or why this difference occurs. What is key from a clinical point of view is figuring out how this information can impact on the treatment of depression, and much more research will need to be done to get to that level. But this is certainly an interesting start. 3/5