Self- groups in the united states are attended by percent of the population each year.

I believe the answer is: 3-4 %

The self-help groups that exist in this country mostly established to specifically tackle a certain disorder (such as alcoholic anonymous, support for the suicidals, groups that teach social skills, etc.) 
While the rest of the people do not necessarily immune to these problems, a large portion of them choose to rely on drugs to manage their psychological problem.