Battlefield 1: I think he got shell shock

In WWI, due to the trench nature of the war, shell shock was a condition that occurred from repeated artillery shelling on fixed positions. Combatants would shell opposing trenches for hours in preparation for ground assaults across what would become known as No Man’s Land. Symptoms included uncontrollable shaking, unrelenting feeling of dread, and overall inability to function. In WWII it went by another name, Combat Fatigue. Today we know it as Post Traumatic Stress Disorder, PTSD. The song is Crazy by Gnarls Barkley and is used for entertainment purposes only; I don’t support piracy, so please make sure to support your favorite artists by purchasing their products legally.

Source: Youtube