That article reads like a hatchet job. It's a lot easier to retain a security clearance than to apply for one when you have. You can argue that's unfair but a lot of intelligence roles are understaffed as is. It's also a very high stress job and a lot of employees turn to alcohol drugs as a coping mechanism.
Also, being sectioned isn't the same as a mental illness. Even PTSD is largely a made up concept.
American soldiers commit war crimes (or witness them happening by fellow soldiers), then years later feel guilty about it. Oh, so you can't stop thinking about that Iraqi family your colleagues massacred you were forced to keep quiet about? That's not guilt you're feeling, you have a mental illness!
Do you know the difference between a soldier feeling guilty and having PTSD? 6 months. The difference between an emotional response and a pathology is completely arbitrary and has no basis in science.
Historically it didn't exist because either soldiers knew what they were getting into, or were fighting a "good" moral war. American soldiers are in a unique position because they actually believe they are signing up for a good and moral cause, yet their actual deployments are like Nazi occupations.
I'd say it's pathological not to have some form of PTSD after a deployment somewhere like Afghanistan and Iraq. Anyone who comes out of those wars with a clean conscious is a psychopath.