Introduction to Mental Disorders

What you’ll learn to do: define mental disorders and explain how they are classified

Black and white photograph of a woman who is hunched over with her hair covering her face and grabbing the back of her hands with her head, depicting anguish.

Mental disorders are conditions characterized by abnormal thoughts, feelings, and behaviors. Although challenging, it is essential for psychologists and mental health professionals to agree on what experiences and actions constitute the presence of a mental disorder. Inner experiences and behaviors that are atypical or violate social norms could signify the presence of a disorder; however, each of these criteria alone is inadequate. It is generally accepted that a mental disorder is defined by significant disturbances in thoughts, feelings, and behaviors. These disturbances must reflect some kind of dysfunction (biological, psychological, or developmental), must cause significant impairment in one’s life, and must not reflect culturally expected reactions to certain life events.

In this section, you will learn about how disorders are defined, and also how they are diagnosed and classified. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) is the most commonly used classification manual that clinicians use to read about the criteria, prevalence, risk factors, and details of over 200 disorders.