On [sic] the main ... we are disappointed with the majority of books on depression. They fail to distinguish between the different types of depression. They waste valuable space debating whether depression is a "disease" like diabetes or a problem of adaptation and poor coping skills. For us, the answer is that depression is a syndrome, with many different causes and solutions.
Most likely, depression is caused by a combination of genetic, biological, environmental, and psychological factors.
Depressive illnesses are disorders of the brain. Brain-imaging technologies, such as magnetic resonance imaging (MRI), have shown that the brains of people who have depression look different than those of people without depression. The parts of the brain involved in mood, thinking, sleep, appetite, and behavior appear different. But these images do not reveal why the depression has occurred [emphasis added]. They also cannot be used to diagnose depression.