Determining Abnormal BehaviorThere are several factors a mental health professional must take into account when trying to determine whether a person's behavior is abnormal. For nearly any type of behavior that you might consider, there is what is called anormal range. People may rank either higher or lower than an average set point, but everything that falls within this range is still considered normal. It is when a behavior lies too far outside of this standard range that it may start to be viewed as abnormal or maladaptive.
Another factor is whether the behavior is distressing to the person. The behavior is only abnormal, however, if the person suffers severe emotional distress or other consequences as a result of the behavior. All people suffer distress from time to time, but this is considered normal. When the behavior becomes extreme or happens on a frequent basis, it is considered abnormal.
One factor is whether the behavior violates cultural standards. Every society has its own set of norms deemed acceptable, and you are expected to conform to those societal norms. Subcultures also have norms; for example, within society in general, wearing extremely baggy pants and bandanas might be seen as abnormal. However, it would not only be considered normal, but would be almost required, in particular subcultures. A behavior that does not conform to the norm of the person's culture is considered statistically abnormal and undesirable. Another factor is whether the behavior is harmful or maladaptive. If the behavior impedes your ability to adjust to the demands of everyday life, it is considered maladaptive. Of course, a behavior that is dangerous and could lead to the harming of oneself or others is considered abnormal.
Other factors determine whether the behavior is irrational, unpredictable, or inexplicable. In these cases, others cannot understand a person's behavior. For instance, someone with anorexia may look as thin as a rail to an outsider, but she believes she looks fat, so she restricts her eating and exercises excessively. This is an irrational behavior that most people cannot understand. Sometimes behavior takes place for no apparent reason. For instance, a person who shouts obscenities at a complete stranger for no apparent reason is considered to be acting erratically. Such behavior is inexplicable and unpredictable and is therefore abnormal.
Making a DiagnosisMaking a diagnosis of mental disorder isn't as easy as just identifying abnormal behavior. Abnormal behavior can be a symptom of a mental disorder, but it does not automatically lead to the existence of a mental disorder. Certainly everyone has behaved irrationally before, but that doesn't mean we all have a mental disorder. These are isolated incidents of a temporary state.
A mental health professional must look at abnormal behavior in terms of length of time and severity. If two or more factors of abnormal behavior apply to a person's behavior, then that warrants a closer look. A person is diagnosed with a mental disorder if the abnormal behavior occurs frequently over an extended period of time and it disrupts a person's normal day-to-day living.
Classifying Mental DisordersTo help identify and diagnose mental disorders, mental health professionals have developed a classification system that describes the symptoms of particular mental disorders. This classification system is found in the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association. This manual contains almost 300 different mental disorders classified in sixteen categories: