Humans generally react this way when they are too hot, violent crimes go up in heatwaves, there are so many variables as to why one person would react more strongly than another to the heat. I had a very low tolerance for heat before I went travelling, 23 degrees c I would sweat and become irritated, now I can easily stand 35 degrees c
I recommend that you wear a hat that shades your neck when outside, direct sun exposure to the neck can case sun stroke, stay hydrated by drinking a small amount of fluid often, remember you get dehydrated before you feel thirsty, also make sure your salt intake is good, when you sweat you lose salt and electrolytes, this will cramp your muscles but it can also cause psychological imbalance.
Acclimation does make things like heat go from feeling like misery to a trivial discomfort. I've noticed after years of living in hot places that a lot of the people who say they are heat intolerant make little effort to become acclimated, instead being in the A/C all day, from home, to car, to office, to back home. When big heatwaves or power outages come along these people are more miserable than they should be. Having seen men in the grips of 105-degree heat stroke, I also agree that dehydration and electrolyte loss from heavy sweating can have profound effects on the human brain and in more mild cases certainly manifest in depressed mood and fatigue.
In this case, a severe loss in electrolytes could effect the cardiovascular system and ion channels in the brain and you might see a drop in blood flow to the brain causing fatigue and neurotransmitter networks disrupted by impaired ion channels manifesting as secondary depression or other psychological issue. One would thus expect the issue to clear up when electrolyte balance is restored, versus primary depression or other psychiatric condition where the person will have had the condition whether or not heat stressed - which is to say the condition might be worsened by heat stress.
FWIW, I love the heat and don't really notice much happens to me from heavy sweating or mild dehydration. Instead, sustained cold temperatures completely suck the life out of me.
Edited by Dichotohmy, 01 July 2017 - 09:08 PM.