This is exactly what a relatively cursory hour or so of research on this matter revealed to me.
Some states have tighter restrictions, many just mirror the Federal Firearms Act of 1968 and the Brady Act.
I personally find the term mental defective extremely derogatory, but that was the terminology in use in 1968.
I strongly suspect in the current witch hunt atmosphere that very ugly things are coming up, and soon.
I don't support ownership in general except in limited circumstances, such as for hunting or recreational or competitive target sports. Hunting doesn't bother me, in fact it can be good, my neighborhood is overrun with deer, in fact a herd of about a dozen crossed the road ahead of me about five am this morning. No hunting here because of the suburban nature.
It seems grossly unfair to take a right away based on class membership - if the same proposal were made to restrict African American males between 18 and 35 , the class population statistically more likely to be involved in gun crimes either as perpetrators or victims, it would never fly. The outrage would be tremendous, rightfully so.
But we will be thrown under the bus, we will be pre-judged without due process, we will be lumped together in databases with sex offenders, common felons and drug dealers, and those databases will be open to improper access without adequate safeguards, IMHO.
And then, there is the question of how this information will be gathered. Will we be required to register with local, state, or federal law enforcement like sex offenders? Or worse, so will our medical records, health insurance records, and pharmacy records be required to be turned over, in violation of our cuurent privacy and HIPPA rights, and in violation of the trust we place in our our healthcare providers? Will we be required to go to the post office or appear before a local board to register, as I had to do in 1983 with Selective Service?