Is backbiting one's parents and mentioning about them what they dislike - due to their connection to depression - forbidden in psychotherapy sessions? And how can psychotherapy be permissible if it is not free from this type of backbiting?

Backbiting is permissible when there is an urgent need and a legitimate benefit, such as consulting a psychiatrist for treatment and seeking advice from him. There is no harm in mentioning parents or others with what is necessary for treatment, provided that it is not expanded upon; because the original ruling on backbiting is prohibition.