it depends on whether a person needs psychotherapy (has a mental illnesses) or just needs councelling for problems (due to external situation).
problems don't go away by themselves and one may need to turn to some sort of advice, such as a marriage councellor or other or a self-help book or even an experienced elder. people do need someone's advice and while the Quran is perfect, it's not necessary that one finds the solution there not because it's nt there but because the human mind overlooks unless they are clearly told, you should do such and such. in this case, i am unsure how successful self-help books are.
human beings are not self-sufficient; we need guidance. we need someone to tell us, make us see the situation through another eyes. sometimes someone else understands the situation better and has better advice than the one who is suffering from it.
on the other hand, for mental disorders one might need to go to a psychotherapist. how helpful they are is a mystery as i have no knowledge of this field. for such health problems, it may be possible that reading the Quran, closeness to Allah, and ruqya will cure the problem. this is because that is an illness.