Skip to Content

Abnormal Psychology: Definition and Examples

Abnormal psychology is an area that focuses on people who exhibit behaviors that are considered atypical compared to a norm group. When most people hear the word ‘psychology,’ abnormal psychology is probably what immediately springs to mind.

Psychological disorders, psychotherapy, and psychiatric treatments are all subtopics related to the field of abnormal psychology.

What Is Abnormal Psychology?

In order to talk about abnormal psychology, it is important to understand what ‘abnormal’ means. Today, experts recognize that mental disorders are far more common than previously believed.

The National Institute of Mental Health estimates that 1 in 5 Americans over 18 experience a diagnosable mental disorder in a given year. This amounts to approximately 52.9 million people in the U.S. alone.

Of these individuals, NIMH suggests that about 5.6% experience what is considered a serious mental illness. Almost half of these individuals also experience two or more disorders at once.

 What Is Normal and What’s Not?

There are many different ways that we can define abnormal behavior.

Statistical Variation

One method involves statistical deviation or looking at how frequently something happens. If a person exhibits a rarely occurring behavior, it could be said that the action is abnormal.

Deviation From Social Norms

Another method is to look at how the person compares to others in their peer group. Do other people engage in similar actions? If a specific behavior or pattern of behaviors violates social norms, then we tend to think of it as abnormal.

However, it is important to note that social norms tend to change over time. Things that were once considered abnormal by a previous generation may now be viewed as perfectly normal and acceptable.

Impact on Functioning

The impact of behaviors on an individual’s ability to function also plays an important role in identifying abnormal behavior. When maladaptive actions interfere with a person’s ability to function in day-to-day life or lead to psychological distress, they are often viewed as abnormal and in need of change.

Defining Abnormal

You can probably think of potential problems with each method of defining abnormal behavior. Just because something deviates from a statistical norm does not mean that it is a bad thing. For example, extremely high intelligence would be one example of a quality that lies outside of the statistical norm.

When comparing behaviors to specific social ideals, you might wonder exactly whose ideal we are talking about. What about social norms that vary based on factors like sex, age, socioeconomic status, or culture? The fact is that no single definition of abnormal behavior will ever be perfect.

Topics of Abnormal Psychology

The primary goals of abnormal psychology include learning more about the causes of mental illness and finding ways to help people suffering from psychological disorders. Some of the major topics of interest within this branch of psychology include:

  • Defining specific mental illnesses
  • Identify specific psychological disorders
  • Developing treatments for mental illnesses
  • Understanding the causes of mental illness
  • Utilizing psychotherapy and medications to treat psychological disorders

Study Questions About Abnormal Psychology

As you are studying the topic of abnormal psychology, think about how you might answer the following questions.

  •  What are some of the key ways that we define abnormality?
  • What are some of the major purposes of abnormal psychology?
  • How can studying abnormal psychology help us better understand how to treat mental illness?


National Institute of Mental Health. Mental illness.

Kessler RC, Chiu WT, Demler O, Walters EE. Prevalence, severity, and comorbidity of twelve-month DSM-IV disorders in the National Comorbidity Survey Replication (NCS-R). Archives of General Psychiatry, 2005 Jun;62(6):617-27.