Substance abuse to get ahead is nothing new. Drugs are not as new as we pretend they are, and it's been common practice to abuse them for personal gain probably as long as they've been around.
Drugs may enable and perpetuate this behaviour today, at least in some countries, but I don't think there's much of a case that they caused it. At least if they did it arose in places like the UK without that assistance.
From my experience the root is far simpler - greed. They dangle the possibility of partnership with all it's attendant wealth and status in front of the bright young things and watch them scrap it out and burn out. I have a friend who made partner with one of the magic circle firms and while the rewards are amazing, I wouldn't swap his life for mine in a million years.
It used to be that about 5% didn't make partner. It was like getting fired-- in the 1970s, when that itself was rare. It was harder to get an associate position, but once you were in, you were solid. Also, work hours were not at the extreme that they are now.
Now, instead of 5% not making partner, it's about 5% who make partner.
That's because some really evil, greedy fucks got in charge and realized they could replace partnerships with overworked, churn-and-burn associates.
Or could it be that there are way too many lawyers being produced every year and the realities of a highly competitive market have set in?
http://flustercucked.blogspot.com/2010/07/40-years-of-lawyer...
The upside (at least for those competing) is that many who don't make partner will still go on to secure corporate lawyer jobs earning six figures...
The industrial revolution was a shift in the curve. You could successfully argue that automation to get ahead is nothing new, but it would miss the importance of the scale of the new changes.
Adderal and its ilk are a similar shift in the curve. People with access used to be people rich enough to afford speed.
Now almost all school kids are entering the work force and know someone or have themselves used performance enhancers.