Medical, biological, and psychological factors are all at work in major depression. The physical symptoms mental slowing, poor concentration, intrusive thoughts, disturbed sleep, change in appetite, decreased energy, decreased sexual interest, body pain, and disrupted body rhythms demonstrate that depression is a physical process. The depressive thoughts of pessimism, worry, self criticism, distortion, and death are clearly psychological.
It is unfortunate that the word depression is used to describe both a medical disease and a bad mood. Some people confuse the two and think that the significant physical, mental, and emotional deterioration caused by major depression is no more serious than a bad mood. Anyone who has suffered from the disease of major depression knows that there is little similarity between the two.
This linguistic mix up contributes to some myths surrounding major depression. After all, if you’re just in a bad mood, people wonder why you cannot exert some effort and pull yourself out of it. However, you usually cannot pull yourself out of major depression; it can be severely debilitating and too often results in death by accident or suicide. People do not kill themselves because they are in a bad mood.
There are even other, different medical conditions that have the word depression in the title, like bipolar depression, organic depression, etc. To keep everything straight, in this book we will often use the correct term unipolar major depression so there is no question of what we mean.