A huge difficulty is distinguishing between actual pathology, as opposed to personality and situational factors. Even if there is a pathology, you need to assess severity and distinguish depression from from transient moods, dysthymia, bereavement… Moreover, form many mental health conditions, subjective allegations are a major - if not the primary - source of diagnostic information. I readily acknowledge that there are some folk who are unable to perform any work due to mental impairments such as depression and PTSD. My personal, non-medical opinion, tho, is that a far greater number of people could work, but for various reasons do not.
Life is hard for just about everyone. I’d suggest it is a rare individual who does not occasionally wake up and feel like they don’t want to get out of bed, or dread going in to work on Monday. Lots of jobs are stressful and unrewarding. Yet, the majority of folk find a way to drag themselves out of bed and do what they need to do.
Others find someone to enable them - or a source of funding other than employment. Or, relatively few decide to take themselves out.
It is also difficult to factor out numerous factors. Hell, the job market is tough enough for someone with an education, work history, lack of criminal record… Subtract any of those, and you make the job search tougher. Add in relationship stresses, poor financial choices, and life gets tougher and tougher. Also, factor in the environment. Millions of Americans are raised in shitty households, with substance abusing, neglectful, uneducated, and abusive, or absent parents. If your life sucks, it would be surprising if you WEREN’T depressed to some degree or another. Then there is the mistaken belief that everyone’s life ought to be as portrayed on TV and in advertising, where everyone in young, beautiful, wealthy, and happy, and no one ever cleans a toilet.
In my opinion, the most persuasive instances of mental health disability are ones in which someone previously was functioning at a reasonably high level - making decent money, then stopped, and not due to a lay off, firing, etc. Also, not everyone who gets fired later gets to say, “Ooh - it was because of my mental impairment!” Some folk are just shitty employees, or fuck up, and deserve to be fired. Again, bad choices.
And some folk lack realistic expectations. Take the ex-teacher in the OP. OK, maybe he can’t handle the challenge of being a teacher Doesn’t mean he couldn’t push a broom, or flip burgers. And what do we do when our economy has so many jobs that are so undemanding and unrewarding?
Allegations/diagnoses of bipolar or episodic impairment can be especially troublesome. Hard to accept that your neighbor is unable to work, when their family just got back from a vacation. Some people do cycle. IMO, many others simply have mood swings which are within the range of normal, and the prefer not to do things they do not find attractive.
There is SOME appeal for folk in lousy situations to present themselves as victims. Far more attractive to persuade others that one can’t help their situations, as opposed to acknowledging that they are fuck-ups. In my experience, I find most refreshing some of the ex-cons and ex- substance abusers I encounter, as they at least take responsibility for their situation.
Don’t minimize the fact that MANY folk and industries benefit from the identification and treatment of mental health issues. The psychologist who writes that someone is “unemployable” is getting paid for his/her services, as does the lawyer representing disability claimants. Health care institutions and bureaucracies have incentives to inflate the size of their clientele, and the need for their services. There are tons of groups on-line and in-person where folk who wish to present themselves as impaired can find support and affirmation. Some improve as a result - many others simply fine-tune their “resume” presenting themselves as disabled both to themselves and the world.
Hugely difficult issues. Ones I’m not at all convinced American society is dealing with well.