Guessing the parents spent too much time/attention on work and not enough on their kids. But these are difficult times, and many folks are struggling to find work and feeling despair even if they otherwise have no major struggles.

Also, I suspect a lot of folks think of substance abuse as a class issue - if you just had more education and a better job you wouldn't be around the low-class folks who do drugs - and take no account of upperclass people doing more expensive street or prescription drugs and more expensive booze.