To be considered a "mental health professional," a person generally must have an M.D., Ph.D. or M.S.W. Some "experts" have an "M.S., P.D." which means they have a Master's degree plus 30 credits -- but have not earned a Ph.D. These people are generally not considered professionals under the law.
The Encyclopedia of Associations (available as a multi-volume hard cover, on the Gale Directory Library, and on Lexis (ENASSC)) lists many groups of mental health professionals.