This has been on the law books since the passing of the 1968 Gun Control Act. There is a section about being "adjudicated as mentally defective". THis is also asked on the 4473 FFL paperwork that you fill out when purchasing a new weapon. It's question 11 - f "Have you ever been adjudicated mentally defective (which includes a determination by a court, board, commission, or other lawful authority that you are a danger to yourself or to others or are incompetent to manage your own affairs) OR have you ever been committed to a mental institution?"
For vets concerns. If you have had a judgement like a BVA hearing and it was deemed that you have a mental disorder and the judgement / doctors have stated that you cannot handle yourself or your own affairs then you are prohibited in owning a firearm.
Also, on SECTION IX - COMPETENCY BVA DBQ questionnaire, question 9 asks "IS THE VETERAN CAPABLE OF MANAGING HIS OR HER FINANCIAL AFFAIRS?" if it's a no then this is the keyword that you will likely lose your second amendment rights. During my C&P I was asked if I handle my own finances. I simply stated "yes" I pay all the household bills.
I have heard some horror stories of friends brothers cousin lost all his guns. There is also a letter floating around the web where the VA mailed to a vet and said something like he had to give up his guns. The thing is, I don't know his entire story on why he had too.
Now...If you are rated at 100% PTSD then it's very likely your guns will go bye-bye.
Total occupational and social impairment, due to such symptoms as: gross impairment in thought process or communication; persistent delusions or hallucinations; grossly inappropriate behavior; persistent danger of hurting self or others; intermittent inability to perform activities of daily living (including maintenance of minimal personal hygiene); disorientation to time or place; memory loss for names of close relatives, own occupation, or own name …………………..100%
Underlined and bold you see where those buzzwords indicate the inability to handle your own affairs. That means you can't brush your teeth or pay your own bills...nor own a Glock.
But the VA is tricky. And the way a rating officer will rate you often doesn't make sense. For instance, I am rated at 70% for PTSD. My DBQ only looks like I should be rated in the 30-50 range. The RO took into considerations I have sleep issues and migraine headaches and lumped those in. Now, I was denied my claim for Migraines as there wasn't a service connection. But these are often a secondary condition of PTSD.
So you could accidentally get rated higher and possibly lose 2A rights. It's a long shot, but still possible I suppose.