An attorney is not required for completing your initial application. However, in the event your application is denied, hiring an attorney to appeal the denial of your claim is strongly encouraged.

After you have submitted your application you will be required to attend a mental health evaluation at a Social Security Administration (SSA) authorized facility with an SSA-approved mental health clinician. If you are including medical diagnoses on your application, you will be required to attend a second, separate evaluation (similar to an annual physical), again with an SSA-appointed clinician.

Personally, I applied under both medical and mental health diagnoses in 2016. My application was accepted 5 months later and I did not need to hire an attorney. There is a recent post on this sub from an individual who submitted an application based on disability caused by mental illness alone, and was successful receiving benefits after their first application attempt; they did not hire an attorney.