The case study is about Diana who suffered from obsessive-compulsive disorder (OCD) for 26 years, but finally overcame it with the help of cognitive behavioral therapy (CBT). The paper discusses the effectiveness and strengths/weaknesses of CBT in treating OCD. CBT is a collaborative, efficient, and ongoing therapy that focuses on identifying root causes of disease. While it has some weaknesses, such as being costly and focusing too much on positive thinking, it remains an effective treatment for many patients.