The idea is that depression is a relationship between the client (the Self) and the idea of his/her parents in his/her head (the Object). When the client is depressed the Object is harsh or neglecting.
Therapy works on incorporating a nice, supportive, encouraging, capable therapist into the picture of the Object in the head. So the client relates to a much nicer Object, thus is not depressed anymore.
So that’s why information about depression is only helpful to a certain extent. The final cure is a relationship that is encouraging.
Often when someone asks for information about depression, they are saying in essence that they are skittish or nervous about starting a relationship with a therapeutic authority figure, because the Object they carry around in their head is so harsh, that they are pretty sure the therapist will be equally harsh or neglecting. It is refreshing to the client when they find out the therapist is not like that at all.