Since the invention of the new generational antidepressant drugs in the 1990s, the biological model of depression prevailed over its alternative explanations. This happened in spite of the fact that at the same time there has been a significant increase in the number of patients treated for depression. The increased presence of depression in everyday life suggests that the change in the explanatory model also altered the way mental health professionals and lay people understand depression. Moods and behaviors previously considered as "normal" are now regarded as mental illness. How to understand the widespread adaptation of the biological model in a sociologically, anthropologically meaningful way? This is the central question of this book. In the book, it is discovered how the following actors relate to the biological model of depression: a group of scientists debating over depression treatment, the different actors (patients, doctors, psychologists, administrators, social workers and nurses) on a psychiatric ward in a mental hospital (2), and eight patients diagnosed with depression. This book aims not only at social researchers interested in the medicalization process, but also at psychiatrists and lay people who are concerned with the problem of depression treatment.