I felt the need to clean my room at home in Indianapolis every Sunday and would spend four to five hours at it. I would take every book out of the bookcase, dust and put it back. At the time I loved doing it. Then I didn’t want to do it anymore, but I couldn’t stop. The clothes in my closet hung exactly two fingers apart…. I made a ritual of touching the wall in my bedroom before I went out because something bad would happen if I didn’t do it the right way. I had a constant anxiety about it as a kid, and it made me think for the first time that I might be nuts.

Whenever I get depressed it’s because I’ve lost a sense of self. I can’t find reasons to like myself. I think I’m ugly. I think no one likes me…. I become grumpy and short-tempered. Nobody wants to be around me. I’m left alone. Being alone confirms that I am ugly and not worth being with. I think I’m responsible for everything that goes wrong.

Voices, like the roar of a crowd, came. I felt like Jesus; I was being crucified. It was dark. I just continued to huddle under the blanket, feeling weak, laid bare and defenseless in a cruel world I could no longer understand.

Now and then, all of us feel, think, or act in ways that resemble a psychological disturbance. We get anxious, depressed, withdrawn, or suspicious, just less intensely and more briefly. So it’s no wonder that we sometimes see ourselves in the psychological disorders we study. “To study the abnormal is the best way of understanding the normal,” said William James (1842–1910).

Either personally or through friends or family, many of us will know the confusion and pain of unexplained physical symptoms, irrational fears, or a feeling that life is not worth living. Worldwide, some 450 million people suffer from mental or behavioral disorders (WHO, 2010). The National Institute of Mental Health (2012) estimates that 26 percent of adult Americans “suffer from a diagnosable mental disorder in a given year” (TABLE 13.1). Rates and symptoms vary by culture, but no known society is free of two terrible disorders—major depression and schizophrenia (Baumeister & Härter, 2007; Draguns, 1990a,b, 1997). This chapter examines these disorders and others. Chapter 14 considers their treatment. First, though, let’s address some basic questions.