Chapter 1: Defining & Classifying Abnormal Behaviour

Summary and Self-Test: Defining & Classifying Abnormal Behaviour

Alexis Bridley & Lee W. Daffin Jr.; Carrie Cuttler; Rose M. Spielman, Kathryn Dumper, William Jenkins, Arlene Lacombe, Marilyn Lovett, & Marion Perlmutter; and Jorden A. Cummings


Mental illness has a significant social and economic cost on society, both directly and indirectly through costs like victimization, lost ability to work, burnout, hospitalizations, and medical visits. Abnormal psychology is a field of psychology that studies people who are atypical or unusual. The intention of this study is to predict, explain, diagnose, identify the causes of, and treat mental disorders.

Mental disorders are hard to define. Most definitions include the “3 Ds”: Dysfunction, distress (or impairment), and deviance. Meaning that disorders disturb an individual’s cognition, emotion regulation or behaviour, that this causes distress for the individual, and that this behaviour is a move away from what our culture determines is normal, typical, or average.

It is important to consider culture when evaluating abnormal behaviour. Violating cultural expectations is not, in and of itself, a satisfactory means of identifying the presence of a psychological disorder. Behaviour varies from culture to culture, so what may be expected and appropriate in one culture may not be viewed as such in others.

In order for a mental health professional to effectively treat a client (and know if the treatment is working), they must first know what a client’s presenting problem is. Clinical assessment refers to collecting information about this and drawing conclusions through the use of observation, psychological tests, neurological tests, and interviews to determine what the symptoms the client is presenting with. The concepts of reliability, validity, and standardization are key to the assessment process.

After the assessment is complete, a professional can consider if the person meets criteria for a clinical diagnosis. Diagnosis is the process of using assessment data to determine if the pattern of symptoms the person presents with is consistent with the diagnostic criteria for a specific mental health disorder, set forth in an established classification system like the DSM-5 or ICD-10. Symptoms that cluster together on a regular basis are called a syndrome.

Classification systems for mental disorders provide health professionals with an agreed-upon list of disorders, for which there are clear descriptions and criteria for making a diagnosis. The most widely used classification system in North America is the Diagnostic and Statistical Manual of Mental Disorders, currently in its 5th edition. It is published by the American Psychiatric Association. The first edition of the DSM was published in 1952 and the current edition was published in 2013 after almost 14 years of research! The World Health Organization (WHO) also publishes the International Classification of Diseases (ICD), an alternative classification system.

The DSM also states the key elements of diagnosis, which include diagnostic criteria and descriptors, which are guidelines for making a diagnosis. A second key element are subtypes and specifiers, used to better characterize an individual’s disorder since the same disorder can manifest in different ways for different people. Last, principle diagnoses are given when more than one diagnosis is applicable for one individual and provisional diagnoses are given when not enough information is available to make a definitive diagnosis.




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Abnormal Psychology Copyright © 2020 by Alexis Bridley & Lee W. Daffin Jr.; Carrie Cuttler; Rose M. Spielman, Kathryn Dumper, William Jenkins, Arlene Lacombe, Marilyn Lovett, & Marion Perlmutter; and Jorden A. Cummings is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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