I agree with 8thStreet....the answer was a bit over-rationalized, and ended up describing "health" more than "normal".

To borrow the language of statistics..."normal" would be the societal "median", while "abnormal" would be a large variance from the median. Of course it's difficult to ascribe mathematical values to behavioral issues on the individual level. So, it's difficult to measure if a person is at a 10 point variance or 15 points or whatever.

Nonetheless, IMHO it's a cleaner, simpler method to define "normal".

For example, everybody gets angry from time to time. That's normal. Some people get angry more often and react to it in a variety of physical ways. That's a "variance" to the norm. Sometimes an extreme reaction occurs often enough that "anger management" is needed. An even greater variance from the norm.