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The causality dilemma has plagued us since the dawn of civilization. What is the cause? What is the effect? How do we determine the difference between the two? These are questions that seem simple at a glance. Cause is understood to be responsible for effect, but is it as simple as it seems? Which came first, the chicken or the egg? See, I’ve stumped you already. Not so easy, right? The causality dilemma is, well, a dilemma, and has remained so since the beginning of civilization.

However, scientists seemed to have resolved a decade-old mystery of causality. The question of whether depression is the cause or effect of brain damage has finally been put to rest. The answer: depression causes brain damage, not vice versa.

 A diffusion MRI of the human brain

Image source: Callisto Images

A recent study conducted by an international group of scientists has discovered that shrinkage of the hippocampus, a region of the brain which functions in memory, inhibition, and space, plays an important role in causing depression. Comparisons of MRI brain scans of more than 9,000 people showed that those who had experienced multiple depressive episodes had significantly smaller hippocampus volumes than those who had only experienced one incidence of depression. In fact, small hippocampus size was not seen at all in those who had only one depressive episode, suggesting that having a small hippocampus is not a predisposing factor to depression, but rather a consequence.

Other studies involving animal experimentation have also reached such a conclusion. The shrinkage of the hippocampus in animals resulted in a change in memory and behavior, or generally speaking, a loss of function in different regions of the brain.

While the findings from the research have not been applied clinically just yet, the confirmation that depression causes brain damage, and not the other way around, helps decipher the enigma behind depression. Though much more must be uncovered, the knowledge obtained from the study can help scientists develop better treatments for the condition and provides hope that depression can be reversible.

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