How long dose it take to get rid of a pinched nerve in the neck?

okay so my dad has had a pinched nerve in his neck and upper back since thanksgiving of last year and hes had two months of a chiropractor hes still having problems and hes been very depressed lately, he also has a lott of anxiety, its a hard up and down process and hes a painter so its hard. i just really want to know how long it last normally please&thankyou