The Study of Abnormal Psychology

abnormal psychology definitions

Posted October 2019 by Sean Jackson, B.A. Social Studies Education, B.S.I.T.; M.S. Counseling; 8 updates since. Reading time: 8 min. Reading level: Grade 11+. Questions on abnormal psychology? Email Toni at:

Imagine you’re in line at the grocery store and you notice that the person in front of you has a tic – their arms periodically jerk around and their head bobs to the left.

This is a hallmark symptom of Tourette syndrome, one of three tic disorders identified by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5).

People that have Tourette syndrome exhibit abnormal behaviors because most people do not have tics – this behavior is statistically not the norm.

But abnormal psychology is about much more than studying behaviors that affect a minority of people. Instead, it is an extensive field of research in psychology that seeks to better understand why people behave the way they do.

Abnormal Psychology Definition

The most basic definition of abnormal psychology is that it’s the study of behavior, feelings, emotions, and thoughts that deviate from the norm.

On a deeper level, abnormal psychology examines why these thoughts, feelings, emotions, and behaviors occur in the context of biological, cultural, or environmental stimuli.

Though it might sound easy enough to label something as abnormal, this isn’t the case – one of the chief difficulties that psychologists encounter is simply trying to define what is and is not normal.

After all, diagnostic criteria change, and how they are applied also changes.

For example, the original DSM, which was published in 1952, classified homosexuality as paraphilia, or a sexual arousal disorder. In the DSM-II (1968), it was classified as a “sexual orientation disturbance,” and in the DSM-III (1980), it was presented as “ego-dystonic homosexuality.”

Then, in the DSM-III-R (1987), it was dropped altogether, reflecting the changing understanding that homosexuality is merely a variant of normal human sexuality rather than an abnormal behavior.

In the past, abnormality was merely defined as a statistical anomaly, but over the years, psychologists have learned that abnormal behaviors, thoughts, and so forth are the result of a combination of factors – most notably, psychological dysfunction, personal distress, and deviance from social norms.

In fact, the DSM-5 uses these three criteria in its definition of mental disorders:

“A mental disorder is a syndrome characterized by clinically significant disturbance in an individual’s cognition, emotion, regulation or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning. Mental disorders are usually associated with significant distress in social, occupational, or other important activities…”

Let’s examine these three factors of abnormality in closer detail.

Dysfunction, Distress, and Deviance: Determining Abnormality

The DSM-5 is clear that no single definition can capture the breadth and depth of abnormality. However, it does require that certain factors are present – dysfunction, distress, and deviance.

From the standpoint of dysfunction, abnormal behavior is viewed as something that diminishes one’s well-being. Moreover, dysfunction can be overtly studied – a person exhibiting dysfunction will not perform as well as one that is not in a dysfunctional state. This allows psychologists to compare the behavior of a person to what is expected of people in general (or to that person’s behavior in the past) to judge whether dysfunction is present.

According to this point of view, whatever is causing the dysfunction (i.e., a student’s grades drop because of stress at home due to their parents getting a divorce), once the issue is resolved, the dysfunctional behavior will return to normal.

Distress, on the other hand, occurs when a person experiences some sort of disabling condition, which can be in many different realms from social distress to occupational distress to distress related to relationships.

Whatever the case, distress can present as physical pain, such as a crushing headache, as psychological pain, such as anxiety, or both. What’s important to note is that distress alone cannot define something as abnormal. It must present with other factors.

For example, even the most high-functioning, normal adult can experience physical and psychological distress as a result of the death of a pet. Only when that distress leads to dysfunction and deviance can it be considered as a factor in causing abnormal behavior. 

Lastly, deviance refers to behaviors that have departed from the norm. Norms, in this case, refer to “common” or “average” behaviors that have been defined by society, culture, values, customs, and so forth. Therefore, behaviors that lie outside those norms are referred to as deviant.

Note that “deviant” in this context does not necessarily mean “inappropriate” or “bad.” For example, having a genius-level IQ is a deviation from the norm, but is certainly not a bad thing. Openly crying for American men is not typical, yet it is not a bad thing, either.

It’s also important to point out that what qualifies as deviant can change over time. Going back to the example of how homosexuality was diagnosed in early versions of the DSM, what was once viewed as deviant behavior is now widely accepted as part of the norm.

For many clinicians, a fourth criterion, dangerousness, is often used to describe abnormal behavior as well. This isn’t to say that people who behave abnormally are a danger to themselves or others, but if a psychologist is concerned that a person’s abnormal behaviors pose a danger, they have a duty to report it to authorities.

When studying abnormal psychology, there are two primary schools of thought that seek to explain why abnormalities occur.

The psychogenetic theory posits that psychological difficulties cause abnormal behaviors, thoughts, and so on.

So, if we go back to our example of the person in line at the grocery store, the abnormal behaviors they displayed (physical tics) are a result of having a psychological disorder – Tourette syndrome. A psychologist working from this perspective might treat the person’s Tourette syndrome using psychological techniques like psychotherapy.

The somatogenic theory offers a different perspective – that abnormal behavior is the result of a physical illness or biological disorder.

From this point of view, the person in line at the grocery store might have tics because they have brain damage suffered in a car accident. Treatment might involve the use of medical interventions like drug therapy or surgery.

In other words, one theory seeks to explain and treat behavior through the lens of psychology while the other seeks to find biological explanations and treatments for abnormality.

By and large, most psychologists don’t pick a side, but rather see behavior as the result of both psychological and physiological issues.

Common Psychological Disorders

The DSM-5 outlines diagnostic criteria for hundreds of mental disorders. Some, like depression, are highly common. Others, like Trichotillomania – an obsessive-compulsive disorder in which a person has a compulsion to pull out their own hair – is much less common.

To organize psychological disorders, the DSM uses broad categories to group similar disorders. Among the most common types are anxiety disorders, mood disorders, psychotic disorders, eating disorders, and dementias.

Below are examples of each class of these disorders.

Obsessive-compulsive disorders (classified as an anxiety disorder) are characterized by pervasive thoughts and repetitive behaviors. An example is Onychophagia, a body-focused repetitive behavior in which the person cannot control their fingernail biting behavior. Though they might try to stop biting their nails, obsessive thoughts about biting their nails creep in, resulting in continued nail-biting to relieve tension.

Major depression (classified as a mood disorder) is the most common psychological disorder, and is often called “the common cold” of disorders. Depression results in a generally depressed mood most of the time, a lowered interest in pleasurable activities, weight loss or gain, fatigue, feelings of worthlessness or inappropriate feelings of guilt, inability to think or concentrate, indecisiveness, and recurrent thoughts of death or suicidal ideation.

Schizophrenia (classified as a psychotic disorder) is a severe mental disorder in which there is a significant disruption in both cognition and emotion. People that have schizophrenia often have a fractured sense of self, suffer from delusions, have difficulties communicating, experience disruptions in thought patterns and perception, and have psychotic manifestations, such as hearing voices.

Anorexia nervosa (classified as an eating disorder) is a common eating disorder in which a person severely restricts their food intake that results in significantly low weight. This is accompanied by an intense fear of gaining weight and an unrealistic conception of one’s body weight and shape.

Alzheimer’s disease (classified as dementia) is often diagnosed when a person has a major loss of memory as well as a decline in physical and mental functioning. These changes must be both profound and develop over a short period of time.

As noted above, the DSM includes many other less common categories of mental disorders, from neurodevelopmental disorders to dissociative disorders to somatic symptom and related disorders. In each case, the criteria for diagnosis (and for gauging abnormality) are extremely clear.

But, as was discussed earlier, diagnostic criteria change with time and with a better understanding of why people behave the way they do. Though it isn’t a perfect system, it is one upon which psychologists studying abnormal behavior must rely.

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