Are NHL enforcers' addictions, depression a result of on-ice brain trauma?

Not so sure of that, a terrible coincidence IMO, The Hammer, Mad Dog Kelly, The Tiger and the MANY other "policemen of past eras this never happened to, perhaps there is a chemical connection combined with the depression that 2 of the three are known to have suffered?

You are young, you love hockey and start playing. You're bigger but you don't have that agressive streak, at least no more than the others. At one point, either your skills tank out or your coaches, because of your size, stop trying to develop them and you are pushed into a role you may not necessarily want. But since what you want more than anything is to play hockey, you follow along, realizing this is your only chance.