Mental health is a little like global warming. First you have to figure out what the temperature should be. If you can't define "normal", you can't define abnormal, except for the really pointy ends of the bell curve.
The study summarizing many dozens of studies more than 40 years ago . . . of what was the main thing that resulted in effective functioning adults had this definition of successful adulthood:
1. Stable job
2. Stable marriage
3. No trouble with the law
4. Not on welfare.
Certainly many people could fulfill those criteria and still be quite crazy.
BTW,
The ONE THING that turned out to account for 80% of the factors resulting in success as adults was . . . drum roll . . . NOT whether the individual was loved by their parents . . . but whether the child FELT loved by the parents. Socioeconomic status, education, types of discipline etc. were all rather minor in discriminating between success and failure as an adult.One definition of mental health is to be grounded in reality--whatever that is. LOL.
i.e. their perceptions, responses, conclusions are not outrageously askew from those of the average person.
But we could get into a book length discussion on what "normal" vs "abnormal" constituted.
Most folks have a round notion that serves fairly well in life most of the time.
Pastors turned out to be good at screening for schizophrenia about as well as most psychiatrists . . . in more than one study.