Now and then, all of us feel, think, or act in ways that may resemble a psychological disorder. We feel anxious, depressed, withdrawn, or suspicious. So it’s no wonder that we are drawn to try to understand disturbed psychological states—we sometimes see ourselves in the mental illnesses we study. “To study the abnormal is the best way of understanding the normal,” said William James (1842–1910).

Personally or through friends or family, we may experience the bewilderment and pain of unexplained physical symptoms, irrational fears, or a feeling that life is not worth living. Among American college students, 1 in 3 report an apparent mental health problem (Eisenberg et al., 2011).

Worldwide, more than half a billion people live with mental or behavior disorders (WHO, 2017a). Although their rates and symptoms vary by culture, no known society is free of two terrible disorders—major depressive disorder and schizophrenia (Baumeister & Härter, 2007; Draguns, 1990a,b, 1997). This part examines these and other disorders. Unit 8, Part II considers their treatment.

Myers' Psychology