It sounds like someone with Multiple Personality Disorder. I would take them to a psychiatrist for an evaluation. People who have endured a lot of pain in their life develop multiple personalities. I wish you all the best! It would be intersting to hear back on what you find out as you may help someone else. Take care.
Sounds very strange, what languge has replace the native one?Was the person concerned a linguist before the event concerned. Would like to know details.Best wishes. George
Don't rule out demonic oppression. Doctors will dismiss this because to them, you're just a piece of meat - no spirit. You (and everyone else human) are first a spirit being, then an immortal soul which resides in a physical body. Your body is temporary, like the Hebrew tabernacle was. We can inadvertently invite a (or multiple) demon(s) into our soul through many, many kinds of activities... including use of tarot cards, palm reading, drugs, dabling in the occult, etc. Also, the spiritual aspect of Yoga is at best suspect as well as martial arts(esp. in advanced degrees). Did they know this other language as a second language already? Find a deliverance ministry in a reputable church (not Catholic - they assign bigger demons to cast out weaker ones and the patient is then much worse off!) and seek spiritual help.