@misc{oai:kawasakigakuen.repo.nii.ac.jp:00000376, author = {Masatoshi TAKEDA and Keigo SHIRAIWA and Kayo MATSUO and Takako NAKAMATSU and Aoi ASHIZUKA and Keiko SAKAI}, month = {Dec}, note = {Depression has long been a major target of psychiatry. The number of patients with depression is increasing year by year, especially in developed countries, and it continues to be one of the most urgent matters for mental health professionals. Efficient treatment measures and useful means of prevention of depression are highly anticipated from the field of psychiatry, but difficult problems in diagnosing and defining depression remain. Since the introduction of the operational diagnostic criteria of Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) in 2013, the diagnostic window for depression has been significantly expanded. Depression from physical cause and depression due to psychosocial cause are no longer distinguished, a situation which may actually hinder the understanding of the pathogenesis of depression. In this review article, inflammation and insulin resistance are used as examples of the physical causes of depression, demonstrating that some depression can be understood as a physical disease. Vascular depression is a physically induced form of depression seen in elderly people, but diagnosis is complicated by depression also being caused by psychosocial factors resulting from various loss experiences associated with old age. Finally, to demonstrate the heterogeneity of depression, we propose a model in which depression develops due to an increase in the amplitude of mood swings, a decrease in the baseline level of mood swings, and a narrower allowable range of mood swings, which can be explained by physical, psychological and social factors, respectively. “Depression is the most unpleasant thing I have ever experienced.... It is the inability to imagine being well again. It is a lack of hope. The emotional depression of major depression is very different from feeling sad. Sadness is a healthy feeling, a need to feel, but depression is quite different” (Rowling JK, 2000), REVIEW ARTICLE}, title = {Is depression a somatic disease or a psychiatric disorder?}, year = {2022} }