The triggers are alcohol, boredom and depression. Alcohol is the worst trigger! I would say that he needs to keep himself busy to keep his mind off it and stay away from the pub/mates who do it etc.
In regards to cheating- men normally can not get it up when on it but it can sometimes make you horny. Other times you’re too dazed to even think about sex. You can not stop talking and sometimes talk absolute nonsense for the sake of talking!