Psychiatry residency is not adult residency its general psychiatry residency, that means gero, forensics, addiction, C&A, C&L etc are all capable jobs. And people do land these jobs or have practice niches that include these. My residency had excellent C&A rotations that I would feel comfortable treating 13yo and up. However, personally, I loathe C&A and simply only do 18 and up.
But to answer your question, there are numerous Psychiatrists who do treat say 13+, or 16+, etc. The younger you go, IMO, the less likely you are to see a non-fellowship trained person doing it. I do believe there is a reason why C&A is a 2 year fellowship and is truly worthy of being its own specialty. The key will be to simply cherry pick the simpler, easy cases, and refer anything else to C&A. Some geographic locations, that just isn't feasible to restrict to 18+, and you will be it as your neighbors beat down your door. Once you do get one C&A in a geographic proximal spot, you can then unload your caseload. Other options if possible are to find a C&A and have them do the initial consult, and you do the follow up work. The bigger liability concern will be med side effects. So, do thorough R/B discussions, get signed consent forms, provide written educational material, etc.
I believe it is sad, wrong, and complete disgrace for our country to permit ARNP doing full spectrum psychiatry with C&A cases. I wouldn't want my own family to be treated by an ARNP for C&A work, I just can't recommend them to others either.