According to the DSM-5 (as cited in Brindley and Daffin, 2018, Module 1.1.2) the 3 D's are dysfunction, distress, and deviance.
Dysfunction - when an individual suffers from a significant disturbance in their cognition, emotions, or behavior in their developmental, biological, or psychological functioning.
Distress - a disabling conditioning in an individual's occupational, social, or important activities.
Deviance - when an individual is behaving in such a way that is not considered normal in relation to what is considered acceptable by society.
Dangerous is the fourth D that