Researchers from the University of Sydney and other academic institutions around the world have discovered that the brain of people who suffer from severe and recurrent bouts of depression have a significantly smaller sized hippocampus compared to healthier individuals.

The hippocampus is a major part of the brain that is responsible for creating new memories for humans and other vertebrates.

The new research, known as the ENIGMA study, is the largest one of its kind to compare the volumes of brains in both people with major depression and those without it. It underscores the need to properly identify depression and effectively treat it on its onset, especially among teens and young adults.

The researchers examined clinical data as well as brain scans using magnetic resonance imaging (MRI) from 1,728 individuals diagnosed with a major form of depression and 7,199 healthy participants. They combined 15 datasets gathered from Europe, Australia and the United States.

The results confirm that the hippocampus of people suffering from major depression is indeed much smaller as first suggested by an earlier study at the Brain and Mind Research Institute (BMRI). People who experienced chronic depression represented around 65 percent of the participants of the research.

The latest study also shows that young people who experience an early onset of depression before reaching 21 years old also had a smaller hippocampus than those who did not have the condition. This supports the notion that these young patients go on to develop chronic disorders.

Participants who experienced an initial episode of major depression, however, were shown not to have a smaller hippocampus compared to healthier people. This number represented around 34 percent of study participants.

The researchers believe this suggests that changes on the brain are caused by the adverse effects typically associated with depressive illness.

Jim Lagopoulos, an associate professor from the BMRI and a co-author of the study, said that the findings provide new insight on the structure of the brain and the potential mechanisms that trigger depression in people.

He explained that despite intensive study aimed at determining specific brain structures connected to depression in previous decades, the understanding of scientists regarding the causes of the condition remains rudimentary.

Lagopoulos said that this is because of the lack of enough large-scale studies, the variability of major depression and the treatments provided and the complexity of interactions between brain structures and characteristics shown in clinical studies.

The researchers believe the findings show the importance of addressing the initial episodes of depression, especially among teens and young adults, in order to prevent the brain from suffering changes associated with chronic depression.

The multi-organizational study is featured in the journal Molecular Psychiatry.

Photo: Allan Ajifo | Flickr 

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