Earlier quoted context omitted.
This is key. Meditation is not a substitute for therapy or professional mental health of any sort.
This doesn't match my experience. Professionals can help you only to the extent they understand themselves. Do they understand nature of consciousness, mind, thought? Most likely they do not. Meditation is supposed to bring one to the state where you get control over those things and if it happens there is no question of mental issues for this person anymore.
What meditation does to the mind is not completely separated from the mental health, but it's not on the same line either. Understanding the nature of your mind heals only minor neuroses, and sometimes with depression.
You can be mentally ill and still have "prajna wisdom" or being "realized" in a very fundamental way. "Prajna wisdom" does not translate directly into normal wisdom or mental health (can help in some cases). The history is full of mentally ill meditation masters, "funny monks" and "crazy wisdom" that is crazy in real way and just not metaphor.
In religious settings people have tendency to attach attach every good thing to meditation in linear way. Morality, mental and physical health, everything. In reality you get "something completely different" (in the Monty Python way). It can help you in other things but it never solves other problems in your life.