Associate Professor Jim Lagopoulos claims findings reveal novel aspects about brain structures and possible mechanisms involved in development of depression.

The ENIGMA study, co-authored by scholars from the University of Sydney at the Brain and Mind Research Institute (BMRI), states that the brains of people who suffer from repetitive episodes of depression have a significantly smaller hippocampus as compared to healthy individuals.

Published in Molecular Psychiatry, the research is the first largest global study that compared brain sizes of almost 9,000 individuals suffering from major depression.   

Conducting Study

Major depression affects at least one out of every six people at some point during their life. It is regarded to be a severe clinical mood disorder in which various emotions – sadness, loss, frustration or anger – interferes with the normal functioning of an individual. The condition may last for several weeks, months or even years.

Using brain scans developed via magnetic resonance imaging (MRI) and clinical data from people suffering from depression, researchers combined 15 databases from Asia, Europe and Australia. Out of the total people studied, 7,199 were healthy and 1,728 suffered from major depression, out of which 65 percent had recurrent symptoms.

Key Findings

Results highlight the importance of identifying and treating depression immediately when it occurs, especially among teenagers and adolescents.

The main finding of the study was that the hippocampus of people suffering from recurrent spells of major depression was smaller as compared to healthy individuals. These findings corroborate those discovered earlier at the BMRI. It was also seen that individuals who had an early onset of major depression – before the age of 21 – had a smaller hippocampus as opposed to healthy individuals, which confirms the theory that young people grow into adults who suffer from recurring major depression.

However, there were certain individuals who had suffered from major depression only once. They comprised 34 percent of the depressed population and did not have a comparatively smaller hippocampus. This indicates that the changes in the size of the latter occur only after consistent, repetitive episodes of major depression.

Usefulness Of Results

Associate Professor Jim Lagopoulos from the University of Sydney’s Brain and Mind Research Institute claims that these findings reveal novel aspects about brain structures and the possible mechanisms involved in the development of depression.

Highlighting the clinical significance of these findings, Professor Ian Hickie who is the Co-Director of the Brain and Mind Research Institute said, “This international study confirms the need to treat the first episode of depression effectively, particularly in teenagers and adolescents, so that the changes in brain structure that accompany recurrent episodes of depression may be prevented.”

Furthermore, the new link established between hippocampus size and recurrent depression somewhat supports the neurotrophic hypothesis of depression. The latter argues that a variety of neurological mechanisms that occur during chronic depression, such as increased levels of glucocorticoids, induces brain shrinkage.

However, Lagopoulos said that despite such advances, a clear understanding of the causes of depression remains in its elementary stages. He attributed this to a lack of adequate amounts of global data, the variability in disease and treatment, and the intricate interactions between brain structure and clinical characteristics.

He recommends that longitudinal studies that track specific changes in the hippocampus of depressed people will help clarify whether the reported changes in volume are due to prolonged stress or certain other risk factors.