3 D's. That is a very good question! i teach that abnormal behavior is defined by the 3 d's. Distress - the person (or people around the person) must be experiencing some type distress dysfunction - the behavior has to be causing some dysfunction in everyday life (not working, poor relationships) deviance - generally, behavior must be considered not normal for population.
Slows functioning. anything that slows your daily functioning.
What's normal? In order to understand abnormal behavior it has to be studied in the context of what is normal behavior. There is no baseline, in other words for comparison.another way of thinking about it is how much the so-called abnormal behavior impedes the life of the person who is behaving as such. The more impeding behavior is, one could say the more abnormal it is. .