People with recurrent depression have a smaller hippocampus, a new study finds.
The hippocampus is part of the brain most strongly linked to forming new memories.
The study may help to explain some of the typical, but lesser known symptoms of depression.
People experiencing depression have particular problems with declarative memory, which is the memory for specific facts like names or places.
Depression blurs other types of memory as well, including the ability to recall meanings and to navigate through space.
Precisely because of memory difficulties and depressed mood, it can be difficult for depressed people to remember the good times.
The findings about the hippocampus come from a study which looked at the brain scans of almost 9,000 people around the world.
Neuroscientists compared the brains of healthy individuals with those who have major depression.
Major depression will affect at least one in six people in their lifetime.
The condition typically returns for weeks, months or even years at a time.
A handful of the emotional symptoms include sadness, anger, frustration and loss.
There are many other less-known symptoms like sleeping problems and changes to appetite (see: 5 Classic Signs of Depression Most People Don’t Recognise).
Dr Jim Lagopoulos, one of the study’s authors, said:
“These findings shed new light on brain structures and possible mechanisms responsible for depression.
Despite intensive research aimed at identifying brain structures linked to depression in recent decades, our understanding of what causes depression is still rudimentary.
One reason for this has been the lack of sufficiently large studies, variability in the disease and treatments provided, and the complex interactions between clinical characteristics and brain structure.”
Dr Lagopoulos continued:
“This new finding of smaller hippocampal volume in people with major depression may offer some support to the neurotrophic hypothesis of depression.
This hypothesis argues that a range of neurobiological processes such as elevated glucocorticoid levels in those with chronic depression may induce brain shrinkage.
Clearly, there’s a need for longitudinal studies that can track changes in hippocampal volume among people with depression over time, to better clarify whether hippocampal abnormalities result from prolonged duration of chronic stress, or represent a vulnerability factor for depression, or both.”
The study was published in the journal Molecular Psychiatry (Schmaal et al., 2015).
Brain image from Shutterstock