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This question originally appeared on Quora. Answer by Fabian van den Berg, (neuro)psychologist and data analyst trying to figure out where to work.

Brain damage is such a harsh term, it’s not like you will find lesions or hole in your brain if you are negative for a year. But there is a bigger mechanism at work where negativity affects your overall health, which in turn can affect your brain again (humans are full of these kind of feedback systems).

A good example is the relation between stress and the immune system. If you are constantly experience negative emotions you will be subjected to stress and more sensitive to stressful situations, being positive is the best defense against stress after all.

Now things become a bit tricky, and I’m not sure if the image will help or confuse (I should remake it one day) but let’s have a go. If you have stress you release cortisol, the main stress hormone. Cortisol has a variety of effects, including one on the immune system. The immune system is rather large and complicated, so below is only a small part and i’m certainly missing like 90% (I’m not an expert in that field), but it is sufficient for the point. Your immune system is nicely balanced, you have cells that deal with intracellular threats (Type 1) and those that deal with extracellular threats (Type 2). These two types are constantly shifting based on threats, one becomes dominant then settles back into a balance. Cortisol (or stress) kinda messes that up, under the effect of cortisol there’s a shift towards Type 2.

Cortisol has a variety of effects, including one on the immune system. Quora

It is thought that this is in part responsible for things like sickness behavior or physically feeling sick when you are very stressed. This leaves you vulnerable to all sorts of threats and simply having this dominance of one side of the immune systems is just bad for all of you, not just the brain.

Negativity and the stress that accompanies it has also been seen affecting certain stem-cells that causes changes the brain. Rather than doing damage it strengthens certain connections (at least in mice), facilitation the fight and flight system, causing another feedback loop. You need that, sure, but too much of it will just get in the way. It increases risks for mental illnesses like anxiety and depression, will shorten your life, and just makes you weaker in general. The prolonged exposure to cortisol subsequently leads to damage to the hippocampus for example.

So, can negativity cause brain damage? Not directly, but the consequences can cause a domino effect, shifting the balances in your brain and entire body. Everything is fine in the right dosages, a little bit will even help you. Too much or too long on the other hand, often leads to the exact opposite effect.

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