Hypothesis: neural mechanism of psychotherapy for the treatment of Parkinson's disease: cognitive behavioral therapy (CBT), acceptance and commitment therapy (ACT), and Morita therapy?

Cognitive behavioral therapy (CBT) for depression and anxiety, established since the 1960s in the USA, and now in Europe, and all over the world has been found to be effective for treating depression in Parkinson's disease (PD). CBT is further developed to acceptance and commitment therapy (ACT) in Europe and the USA. The neural mechanism of CBT or ACT is still under investigation. In Japan, Morita therapy, a psychotherapy founded in 1919 by Masatake (Shoma) Morita, has been used for common mental problems such as anxiety and depression, but rarely for the psychological symptoms in PD. Morita Therapy is in sharp contrast to western CBT in teaching that undesired mental symptoms such as anxiety and depression are natural features of human emotion in health and disease rather than something to control or eliminate, but it is speculated to be similar to ACT in the approach to acceptance but not elimination of mental symptoms. I speculate that the neural basis might be similar in CBT, ACT, and Morita Therapy. In this commentary, a hypothesis is proposed that CBT, ACT, as well as Morita Therapy might be effective for the treatment of the psychological symptoms such as anxiety and depression in PD and in other mental and physical diseases, probably by similar neural mechanisms in the brain.