A new international study has found that people with recurrent depression have a significantly smaller hippocampus — the part of the brain responsible for forming new memories — than those with a first depressive episode or no depression.
“This large study confirms the need to treat first episodes of depression effectively, particularly in teenagers and young adults, to prevent the brain changes that accompany recurrent depression,” said Dr. Ian Hickie, co-director of the Brain and Mind Research Institute (BMRI).
The research, conducted by University of Sydney scholars at BMRI, is the largest international study to compare brain volumes in people with and without major depression. It highlights the need to identify and treat depression effectively when it first occurs, particularly among teenagers and young adults.
“This is another reason that we need to ensure that young people receive effective treatments for depression, a key goal of our Centre of Research Excellence in Optimising Early Interventions for Young People with Emerging Mood Disorder,” said Hickie.
Using magnetic resonance image (MRI) brain scans, and clinical data from 1,728 people with major depression and 7,199 healthy individuals, the study combined 15 datasets from Europe, the U.S. and Australia.
The findings show that people with an early age of onset of major depression (occurring before the age of 21 years) have a smaller hippocampus than healthy individuals, consistent with the notion that many of these young people go on to have recurrent disorders. Of all the study participants with major depression, 65 percent had recurrent episodes.
However, people who had a first episode of major depression (34 percent of study subjects with major depression) did not have a smaller hippocampus than healthy individuals, indicating that the changes are due to the adverse effects of depressive illness on the brain.
“These findings shed new light on brain structures and possible mechanisms responsible for depression,” said Associate Professor Dr. Jim Lagopoulos of the BMRI.
“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.”
“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,” Lagapoulos said.
The findings are published in the journal Molecular Psychiatry.
Source: University of Sydney