AO3. A strength of CBT is that research evidence has shown its effectiveness in treating depression. March et al found that CBT was as effective as antidepressants. A group of adolescents with depression were given either CBT, antidepressants or a combination of both. After 36 weeks, 81% of the CBT group improved and 81% of the antidepressant group improved. In the combined group, 86% improved. This shows that CBT can help, and that a combination of both treatments may be more effective.