If we are stating that faulty/irrational thoughts CAUSE depression, we must try and change/challenge these thoughts/beliefs in order to treat the depression.
Cognitive treatments for depression are based on the assumption that faulty thinking/thought processes make a person vulnerable to depression.
Cognitive Behavioural Therapy involves both cognitive and behavioural elements.
The cognitive elements aims to identify irrational and negative thoughts which lead to depression.
The aim is to replace these negative thoughts with more positive and rational ones.
The behavioural element of CBT encourages patients to test their beliefs through behavioural experiments and homework.