According to a study out of the University College of London and published in Molecular Psychiatry, a region of the brain that responds to bad experiences has the opposite reaction to expectations of aversive events in people with depression compared to healthy adults. The habenula, a pea-sized region of the brain, functions abnormally in depression. The same team of researchers had previously shown that the habenula was activated in healthy volunteers when they expected to receive an electric shock.
“A prominent theory has suggested that a hyperactive habenula drives symptoms in people with depression: we set out to test that hypothesis,” said the senior author on the paper. “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.”
For the study, the brains of 25 individuals with depression were compared via high-resolution functional magnetic resonance imaging (fMRI) with the brains of 25 healthy individuals. In the experiment, pictures shown to the participants developed an association with either a good or bad outcome – an electric shock. The important revelation was that images predicting electric shocks were found to cause increased habenula activation in healthy volunteers, but decreased activation in depressed people.
While there were no differences in average habenula size between people with depression and healthy volunteers, people with smaller habenulae, in both groups, were found to have more symptoms of anhedonia, a loss of interest or pleasure in life.
“The habenula’s role in depression is clearly much more complex than previously thought,” said the lead author. “From this experimental fMRI study we can draw conclusions about the effects of anticipated shocks on habenula activation in depressed individuals compared with healthy volunteers. We can only speculate as to how this deactivation is linked to symptoms, but it could be that this ancient part of the brain actually plays a protective role against depression. Animal experiments have shown that stimulating the habenula leads to avoidance, and it is possible that this occurs for mental as well as physical negative events. So one possible explanation is that the habenula may help us to avoid dwelling on unpleasant thoughts or memories, and when this is disrupted you get the excessive negative focus that is common in depression.”
This could bring hope in helping those suffering from depression.
Razi Berry, Founder and Publisher of Naturopathic Doctor News & Review (ndnr.com) and NaturalPath (thenatpath.com), has spent the last decade as a natural medicine advocate and marketing whiz. She has galvanized and supported the naturopathic community, bringing a higher quality of healthcare to millions of North Americans through her publications. A self-proclaimed health-food junkie and mother of two; she loves all things nature, is obsessed with organic gardening, growing fruit trees (not easy in Phoenix), laughing until she snorts, and homeschooling. She is a little bit crunchy and yes, that is her real name.
