What Is ADHD?


Attention deficit hyperactivity disorder (ADHD) is a chronic condition characterized by impulsive behavior, inattention, and hyperactivity.

It’s usually diagnosed in childhood, but symptoms of ADHD can continue through adolescence and adulthood, so it may also be diagnosed for the first time in adults. With proper treatment, children and adults with ADHD can live successful, highly productive lives.

What’s the Difference Between ADHD and ADD?

Attention deficit disorder (ADD) is an older term for what’s now known as ADHD. While some people still use the terms ADD and ADHD interchangeably, and may call the condition ADD if a child only has trouble focusing but isn’t hyperactive, ADHD is officially recognized as the correct diagnosis of the condition by the current version of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM).

The condition was commonly referred to as ADD until 1987, when “hyperactivity” was added to the name in the third edition of the DSM. When the revised, fourth edition of the DSM was published in 1994, ADHD was divided into specific subtypes, taking into account the fact that an individual could be diagnosed with ADHD without having symptoms of hyperactivity.

Types and Symptoms of ADHD

There are three forms — or “presentations” — of ADHD, as referred to in the DSM-5. The three are:

Predominantly Hyperactive-Impulsive
People with this type of ADHD mostly struggle with hyperactivity and impulsiveness, although they may also have some symptoms of inattentiveness.

Hyperactivity includes constant movement and excessive fidgeting and talking. In adults, this may take the form of exaggerated restlessness and an activity level that other people find tiring.

Impulsivity involves making important decisions and taking action without thinking through the consequences, especially when those actions might be harmful or detrimental and the resulting effects long lasting.

Impulsivity is also marked by a desire for instant gratification. In social situations, an impulsive person might interrupt others to an extreme degree, and be quick to grow impatient, frustrated, or angry.

Predominantly Inattentive
People in this category mainly have symptoms of inattentiveness, although they may still have some problems with hyperactivity and impulsiveness.

This form used to be (and sometimes still is) called ADD.

Inattentiveness is characterized by struggling to stay focused, being easily distracted from the task at hand, and a lack of persistence or organization. This can result in professional and personal difficulties — a lack of attention to detail and missing important deadlines, meetings, and social functions.

Combined Hyperactive-Impulsive and Inattentive
People in this group have symptoms of hyperactivity, impulsiveness, and inattentiveness. Most children have this combined type; but the most common symptom of ADHD in preschool-age children is hyperactivity.

Children who are hyperactive may talk excessively, squirm and fidget, and have trouble sitting still. In childhood, impulsivity can take the form of impatience, disruptiveness, and difficulty waiting for a turn. Inattention can include daydreaming, difficulty following instructions, forgetfulness in daily activities, and trouble focusing.

In adults, ADHD symptoms may take the form of impulsiveness, frequent interrupting, restlessness, inability to concentrate, a lack of organization and follow-through, difficulty meeting deadlines, frequent mood swings, and struggling to cope with stress.

How Is ADHD Diagnosed?

Though many people lose focus, get distracted, and act impulsively on occasion, these behaviors are more severe and more frequent for people with ADHD. Without proper identification and treatment, these behaviors negatively affect their quality of life, whether it’s at work, school, or home.

There’s no one ADHD test to diagnose the disorder. A thorough evaluation by a professional — such as a psychologist, psychiatrist, pediatrician, or clinical social worker — is necessary for a proper diagnosis, which rules out other conditions and considers possible coexisting conditions.

The process involves several steps, and your healthcare provider may perform a full medical exam and get a detailed medical history, as well as conduct interviews with family members to gather a personal history.

The DSM now requires that ADHD diagnoses include the severity of the condition, from mild to moderate to severe.

Causes and Risk Factors for ADHD

Experts aren’t sure what causes ADHD. Research suggests that the disorder has a strong neurobiological basis and that heredity is a major factor. (11)

Neuroimaging studies using MRIs to look at brain structure have found a consistent set of neural circuits to be associated with ADHD. These circuits are related to sustained attention, control of inhibitions, motivation, and regulation of emotions.

But it’s unclear whether ADHD behaviors result from abnormal neural connections or whether there is neural adaptation because of symptoms.

Imaging studies have shown that certain areas of the brain are smaller in children with ADHD compared with children who don’t have ADHD. Two meta-analyses found that these differences in brain volume are no longer detectable in adulthood, suggesting that ADHD symptoms may be due, in part, to delays in development or maturation.

Several factors may increase a child’s likelihood of developing ADHD:

Genetics appear to play the largest role. ADHD has been shown to run in families, and studies have estimated that heritability may range from 60 to 90 percent.

Although the specific genes at play have not yet been identified, scientists believe multiple genes may be involved, because it’s such a complex condition. (13) These genes may have to do with the processes of certain neurotransmitters, such as dopamine, which plays a role in the brain’s reward systems and in regulating impulsivity and movement.

Environmental exposure to toxins and chemicals, especially to lead, may be a contributing factor. Studies have indicated a relationship between ADHD and levels of lead in the bloodstream. One 2010 study, published in the Journal of Child Psychology and Psychiatry, found that lead exposure was associated with the impulsivity-hyperactivity combined type of ADHD, but not the inattentive type. (14)

Alcohol or tobacco use during pregnancy has been associated with ADHD symptoms in children in a number of studies. But more recent research has questioned whether the use of these substances directly causes ADHD.

A study published in April 2016 in the Journal of Child Psychology and Psychiatry found no support for a causal association between smoking during pregnancy and ADHD. (15) Similarly, a study published in October 2017 in the International Journal of Epidemiology found that maternal alcohol use during pregnancy was weakly, though perhaps causally, associated with reported ADHD symptoms but not with clinical diagnoses of ADHD.

By Lynn Marks Medically Reviewed by Robert Jasmer, MD