Research support implies that CBT is an effective treatment for depression. Ellis (1957) found that REBT has a 90% success rate, taking an average of 27 sessions.However he recognised that some clients did not put their revised beliefs into action (2001)Research suggests CBT may not be appropriate for some individuals.CBT appears to be less suitable for people with high levels of traditional beliefs that are both rigid and resistant to change (Elken et al.,1985)This suggests that there are individual differences.The belief that changing behaviour can go some way in alleviating depression has been found by a study on the beneficial effects of exercise.Babyak et al.,2000 studied 156 adult volunteers diagnosed with major depressive disorder. They randomly assigned to a 4 month course of aerobic exercise, drug treatment or a combination of both. Clients in all 3 groups showed significant improvement at the end of the 4 months.This implies that the behavioural action in CBT helps the process of alleviating depression.