There is no precise definition of Mental Health...
And actually mental health is being "flexible" about things in life rather than "ridged" and "unbending".
So you would be best to accept that there are various views as to what mental health is. And that it does not need to be exact. In my view that would be more "mentally healthy"!
Also I have found that many religions have "agendas" (gaining $$ or power for the specific group of people / church) and that in some cases might not be conducive to mental health - it is an "unbending" thing! i.e. "You
must be this way." Well for one good reason or another, some people
can't be that way. That causes conflict - not good. Not healthy.
An "open mind" and "flexibility" are easier on the "nerves"!
Note: I have nothing against churches or religions. Some of them have some pretty sound ideas and teachings. It is just they sometimes lack flexibility.
Things written many years ago may not apply to modern times...
How about "Halizah" where "...In the presence of town elders, the widow loosens the shoe of the brother-in-law, spits upon the ground before him, and recites a prescribed formula which scolds him for not building his brother's household..."
"...the Biblical law of levirate marriage is still presumed in force, thus making the childless widow who remarries someone other than her brother-in-law without performing the
halizah ceremony an adulterer..."
So things like that pop up in various religions. Here is more on the above...
Halizah - Wikipedia, the free encyclopedia