well it depends on what psychological disorder is being treated, but for a lot of disorders from anxiety to anorexia/bulimia cognitive behavioural therapy is used to challenge the negative thought and break the wrong thought patterns these people have, most therapy involves finding the root cause of the disorder and then working from their depending on what the disorder is. It depends on each individual of what theerspy is likely to be of use to them as each person responds differently to each type of therapy as their is no specific therapy which can be used for each specific disorder or peson. But i'd say C.B.T is very likely the most common one used as i think it's the most effective one, im not a professional though. xXx