Introduction to History, Classification, and Assessment

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.

Why is it important to classify these disturbances into psychological disorders? Classification is important because it allows scientists to identify and group patterns of symptoms. For example, in the case of depression, researchers might be able to identify common factors that help explain the origins of depression. Classification systems used in clinical psychology aim to ease understanding and communication between clinicians and researchers by standardizing the language used around disorders. These systems also allow for consistent and reliable research about the diagnosis, prognosis, and treatment of disorders. The most popular classification system in the United States is the DSM-5, but the ICD-11 is another popular system used internationally.^[1]

Important decisions are made on the basis of classification, such as deciding on which therapy to choose or which drug to administer. Classification is not without its criticism, however. It has the potential to dehumanize by labeling, but it does allow clinicians to better predict behavior—schizophrenia, for example, follows a more or less predictable course.

Once we have established the types of psychological disorders, we will evaluate each client individually to investigate what pattern of symptoms may be present and evaluate whether the individual meets the criteria for a psychological disorder. We will discuss the “clinical method,” or an approach to understanding and treating mental disorders that begins with a particular individual’s personal history and is designed around that individual’s psychological needs. Taking a personal history along with a diagnostic interview allow the mental health professional to fully establish a clinical diagnosis. You will see, as we discuss cases in future modules, that a comprehensive assessment can prove valuable in helping to understand the nature of an individual’s symptoms and potential directions for treatment.

Psychological assessment usually involves a comprehensive assessment of the individual. Psychological assessment can be seen as a formal evaluation of an individual’s cognitive, personality, and psychosocial functioning. The process typically involves checking the integration of information from multiple sources, such as tests of normal and abnormal personality, tests of ability or intelligence, and tests of interests or attitudes as well as information from personal interviews.

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.
• The classification and assessment of abnormal behavior, beginning with the DSM-5.
• Diagnostic tools and assessment tools used to gather information about an individual.