Introduction. Psychotherapy is a type of therapy used to treat emotional problems and mental health conditions. It involves talking to a trained therapist, either one-to-one, in a group or with your wife, husband or partner.sychotherapy can be used to treat a wide range of mental health conditions, including: 1  depression. 2  anxiety disorders. 3  borderline personality disorder (BPD). 4  obsessive compulsive disorder (OCD).