The hippocampus, an area of the brain responsible for memory and emotion, shrinks in people with recurrent and poorly treated depression, a global study has found.
The findings highlighted the importance of treating depression early, particularly in teenagers and young adults, the study concluded.
Fifteen research institutes around the world, including from the US, Europe and Australia, collaborated to combine the results of their existing, smaller studies comparing the hippocampuses of depressed and healthy people.
This allowed them to examine the brain magnetic resonance imaging data of 8,927 people, 1,728 of whom had major depression and the rest of whom were healthy.
The researchers found 65% of the depressed study participants had recurrent depression and it was these people who had a smaller hippocampus, which is near the centre of the brain and is involved with long-term memory, forming new memories, and connecting emotions to those memories.
The findings of the largest international study to compare brain volumes in people with and without major depression were published in the medical journal Molecular Psychiatry.