Who should have the power to define abnormality? Societies (popular vote), political groups, governmental/legal agencies, or mental health professionals?

What might be the advantages and disadvantages to allowing one or all of these groups have the final say?

Mental health professionals and society should have the power to define abnormality. Mental health professionals would be able to tell whether or not something is a disease. The society would be able to tell whether or not something is against the established social norms.

If one of these groups has the final say, then let them have it.

Answer: Governmental/legal agencies,

Explanation: Allowing a government or legal agency to have a say on abnormality will have huge advantages of making the populace see it as very vital the need to maintain normal process of doing things without violating set out laws and order. The disadvantage is that the agency might violate the laws which they have the power to speak against and no one will have the audacity to confront them with full force.