I'm pretty sure that it would have to be a psychiatrist who diagnoses the illness and that's what SSA takes into consideration. Also, if you have applied for SSDI/SSI, they should be sending you to a psychiatrist of their choosing to meet with you and discuss your illness. They will then make a report and send it to SSA.

You may find good help at your local NAMI office or by visiting their site here -

NAMI | Social Security and Disability Benefits

I hope this helps you!