While Amro does have eccentric personalities in its army of Asylums, they will not allow someone whose insanity is driven from alchemical abuse to join the rank. (In all likelyhood, that person would be killed as he/she is a threat of going "insane") 

On the other hand it is possible if your character has certain traits associated with clinical (non alchemy related) insanity. Schizophrenia, he may be a sociopath, he may have homicidal tendencies etc etc. In the end Amro focuses on a few basic characteristic that must be present in an Asylum. The desire to live, the fear of death and the capacity to obey orders.