Our understanding of depression and how it affects the brain has changed drastically over the past several years.
It wasn't all that long ago, in 1895, when we first made the distinction between depression and schizophrenia. As recently as the early 20th century, we were still lobotomizing people (destroying the frontal portion of their brains, which often had dire consequences) as a means of depression treatment at the time.
And it's good that we've come such a long way.
The exciting thing is that we're still learning more and more about depression and its effect on the brain, which will hopefully allow us to treat it better.
A new study conducted by the ENIGMA MDD Working Group has provided a great amount of data showing that persistent depression causes damage to the brain.
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Image: WebMD
The study took a look at 9,000 individuals, the largest sample size of any depression study to date, and observed the hippocampus region of their brains.
The hippocampus region is a major part of the brain that deals with memory, spatial navigation and emotion. The region also houses the amygdala, which has been positively linked to depression by past research.
In the ENIGMA study, MRI scans were taken of 1,728 patients who had been diagnosed with depression. They were compared to images from 7,199 individuals that had not been diagnosed.
The hippocampus in depressed individuals had shrunk by as much as 1.24%.
Professor Ian Hickie, one of the study's authors, says:
"Your whole sense of self depends on continuously understanding who you are in the world – your state of memory is not about just knowing how to do Sudoku or remembering your password – it's the whole concept we hold of ourselves... We've seen in a lot of other animal experiments that when you shrink the hippocampus, you don't just change memory, you change all sorts of other behaviors associated with that – so shrinkage is associated with a loss of function."
The danger with hippocampal shrinkage is that it starts a negative self-fulfilling cycle. Memories become more negative and as a result, a person's expectations for the road ahead become similarly negative.
Shrinkage of the hippocampus is just one example of depression's very real effects on the physical brain. Another study from 2000 found that depression is linked to about 40-50% higher cortisol levels, which is also linked to damage of the hippocampal neurons.