self-medicating

You're not correcting for people who had mental illness before they started taking drugs and are self-medicating.

Are all of those smokers simply making a bad choice, or are some of them self-medicating?

If one doesn't 'tough it out', one is viewed as weak, and this often leads to self-medicating and other related illnesses.

Is it possible that the subjects who went to cannabis already had problems, are self-medicating, and would have achieved the adverse outcomes anyway?

You are describing symptoms of depression and some mild or severe psychotic symptoms, combined with the very risky and assertive decision of self-medicating.

I do have extreme empathy for most alcoholics though, especially the one's that are self-medicating.

More and more, I don't see addicts; I see people self-medicating for undiagnosed neurochemical imbalances.

Were people self-medicating in such a fashion a couple of decades ago when AD(H)D was not well known, recognized, nor treated by the medical establishment?

Most people probably shouldn't treat serious illnesses by self-medicating with powerful drugs, especially those obtained illegally where the purity of the drug might be questionable.

I suffer from attention deficit disorder, but before I was diagnosed I was self-medicating myself with stimulants – coffee and energy drinks.

It's a culture that can't wait to put itself to sleep so it doesn't have to think (see the hyper self-medicating that Americans are doing for example).

Edit: granted, this still can happens when self-medicating.

I don't recommend "self-medicating" on purpose, though...

Then got a little too exuberant around the turn towards forty, probably a combination of "Hey, so this is how it feels to feel good!" + self-medicating for the lingering effects of really bad childhood trauma.

The key word here are, I think, “ going to a doctor ”, as opposed to unsupervised self-medicating, or at least without supervision of a trained and licenced professional.

An important note: the clinical definition of Attention-Deficit Disorder is exactly "being unable to feel motivated, except under conditions of stress/fear/pain." A common self-medicating strategy for people unaware they have ADD, is to invite unhappiness and stress in order to derive motivation from it.