Work stress is often relieved using drink and other recreational drugs and as the stress mounts people are more likely to over indulge. You often don't notice it happening either which is why it is so dangerous: at first you don't drink more per visit you just start drinking after work a little more often - then your body's tolerance to the effects drops so you start needing more to make the same difference. "I think I need an extra one today" soon becomes an extra one every time you do out after work.
It is made worse by our dependence on caffeine to get through long hours. People end up keeping themselves awake in the day with caffeine & sugar and knock themselves out at night with alcohol, which leads to a bad night's sleep meaning more caffeine is needed the next day creating a vicious little circle.
I've been there myself a few times.
We can cope with this for a while, and find it easy enough to "reset" when the stress dies down, but if it goes on too long it pretty quickly it becomes damaging to long-term health and potentially sets you up for an addiction problem.
YMMV of course: some people react quite differently to both stress and drugs.