Funny enough I wrote a piece that explains that. Short version: If you want to find suicide bombers look for people who are suicidal. People with PTSD. And the best indicator of that? Excessive alcohol or pot use. Which may explain why so many suiciders spend their last days getting drunk or stoned - the 9/11 guys being a case in point. http://classicalvalues.com/2015/11/does-ptsd-cause-terrorism/
It is my contention that if we were treating these people instead of hounding them the country would be better off. We might have a lot fewer vet suicides as well. I think there are already 23 med pot states and 4 legal states + DC.The police resources we waste on Prohibition could be better used going after the Islamic nutters. G. Bush post 9/11 wanted to put 1/2 the FBI drug squad into counter terrorism. The bureaucracy vetoed that move. Maybe it is time for the change.
It might be good to keep an eye on heavy alcohol and drug users. But not for the usual reasons. To get them to come forward voluntarily you have to call off the dogs. Besides - how can you make pot prohibition work when 58% (and rising) of Americans are against it? It couldn't work when only 12% were against it.