ADHD, or Attention-Deficit/Hyperactivity Disorder, is a neurodevelopmental disorder that affects both children and adults. It is characterized by persistent patterns of inattention, hyperactivity, and impulsivity that are more frequent and severe than is typically observed in individuals at a comparable level of development.

ADHD is not just a childhood disorder. While the symptoms of ADHD begin in childhood, they can continue through adolescence and adulthood. Despite being a common mental health disorder, ADHD is often misunderstood, which can lead to stigma and misconceptions. This glossary of terms article aims to provide a comprehensive understanding of ADHD, its causes, symptoms, diagnosis, and treatment.

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Definition of ADHD

ADHD is not a one-size-fits-all disorder. It presents differently in every individual, with symptoms ranging from mild to severe. The disorder is divided into three types: predominantly inattentive, predominantly hyperactive-impulsive, and combined type. Each type has distinct symptoms but all stem from the overarching characteristics of inattention, hyperactivity, and impulsivity.

It’s important to note that everyone can exhibit these behaviors at times. However, for someone with ADHD, these behaviors are more severe, occur more often, and interfere with or reduce the quality of social, school, or work functioning.

Further reading: ADHD & Social Anxiety »

Types of ADHD

The predominantly inattentive type of ADHD, previously known as ADD, is characterized by difficulty paying attention, overlooking details, and forgetting things. Individuals with this type may seem to not listen when spoken to, have difficulty organizing tasks, and be easily distracted.

ADHD infographic © Rawhide

The predominantly hyperactive-impulsive type is characterized by symptoms of hyperactivity and impulsivity. Individuals with this type may fidget, have difficulty remaining seated, and interrupt or intrude on others. The combined type, as the name suggests, involves symptoms of both inattention and hyperactivity-impulsivity.

Inattentive Type (previously known as ADD)

The primary symptoms are related to inattention. Symptoms include:

  • Often failing to give close attention to details or making careless mistakes
  • Often having difficulty sustaining attention in tasks or play activities.
  • Often not seeming to listen when spoken to directly.
  • Often not following through on instructions and failing to finish responsibilities (tasks)
  • Often having difficulty organizing tasks and activities.
  • Often avoiding or being reluctant to engage in tasks that require mental effort.
  • Often losing things necessary for tasks or activities.
  • Being easily distracted by extraneous stimuli.
  • Often being forgetful in daily activities.

Hyperactive-Impulsive Type

The primary symptoms are related to hyperactivity and impulsivity. Symptoms include:

  • Often fidgeting with or tapping hands or feet or squirming in seat.
  • Often leaving the seat in situations where remaining seated is expected.
  • Often running or climbing in situations where it is inappropriate.
  • Often being unable to play or engage in activities quietly.
  • Often talking excessively.
  • Often blurting out an answer before a question has been completed.
  • Often having difficulty waiting for one’s turn (e.g., while in line).
  • Often interrupting or intruding on others’ conversations or games.

Combined Type

This is the most common type and includes both inattentive and hyperactive-impulsive symptoms. Individuals with this type exhibit six or more symptoms from both categories.

Common Symptoms

Common symptoms of ADHD include difficulty maintaining focus on one task, becoming bored with a task after only a few minutes, difficulty organizing and completing tasks, daydreaming, being easily distracted, talking nonstop, being constantly in motion, and acting without thinking.

These symptoms can cause significant impairment in various areas of life, including academic achievement, occupational functioning, and social relationships. It’s important to remember that these symptoms must be chronic, cause significant impairment, and not be better explained by another condition to be considered indicative of ADHD.

Causes of ADHD

The exact cause of ADHD is not known, but research suggests that it is likely due to a combination of several factors. These include genetics, brain structure and function, and environmental influences. It’s important to note that ADHD is not caused by poor parenting, excessive sugar, or lack of discipline, as is often mistakenly believed.

Genetics play a significant role in the development of ADHD. Studies show that ADHD tends to run in families, suggesting a genetic component to the disorder. Changes in certain genes that affect neurotransmitters in the brain related to attention and impulse control may be involved.

Brain Structure and Function

Research has shown differences in the size and activity of certain areas of the brain in people with ADHD. These areas are involved in regulating attention, impulsivity, and activity levels. However, it’s not clear how these differences relate to the symptoms of ADHD.

Functional imaging studies have also shown differences in the patterns of neural connectivity and activity in the brains of individuals with ADHD. These differences may underlie the inattention, impulsivity, and hyperactivity characteristic of the disorder.

Environmental Influences

Environmental factors may also contribute to the development of ADHD. These include prenatal exposure to alcohol and tobacco, premature delivery, significantly low birth weight, and high levels of lead in the bodies of young children.

While these factors are associated with an increased risk of developing ADHD, they are not guaranteed to cause the disorder. Many children exposed to these risk factors do not develop ADHD, and many individuals with ADHD do not have any known risk factors.

Diagnosis of ADHD

Diagnosing ADHD is a complex process that involves multiple steps. There is no single test to diagnose ADHD. Instead, a comprehensive evaluation is necessary to establish a diagnosis, rule out other causes, and determine the presence or absence of co-existing conditions.

Such an evaluation typically includes a clinical interview, a medical examination, a review of the individual’s developmental history and current symptoms, and the use of ADHD rating scales or checklists.

Clinical Interview

A clinical interview is a key component of the diagnostic process. It involves a detailed discussion with the individual (and parents, if the individual is a child) about the symptoms, their duration, the degree to which they interfere with various aspects of life, and whether they occur in more than one setting (e.g., at home, at school, or at work).

The clinician will also inquire about other potential causes of the symptoms, such as physical disorders, other mental health disorders, life stressors, and medication side effects. This information helps to rule out other possible causes of the symptoms.

Medical Examination

A medical examination is important to rule out physical disorders that may cause or exacerbate ADHD symptoms. This may include a physical exam, a neurological exam, lab tests, and a review of the individual’s medical history.

While there is no specific test for ADHD, certain medical conditions, such as thyroid problems, sleep disorders, and neurological disorders, can mimic ADHD symptoms. Therefore, ruling out these conditions is an important part of the diagnostic process.

Treatment of ADHD

Treatment for ADHD typically involves a combination of medication, psychotherapy, education or training, and behavioral interventions. The best treatment plan is tailored to the individual’s specific needs and may involve one or more of these components.

It’s important to note that while treatment can help manage the symptoms of ADHD, it doesn’t cure the disorder. ADHD is a chronic condition that requires ongoing management.


Medication is often the first line of treatment for ADHD. Stimulant medications, such as methylphenidate and amphetamines, are the most commonly used medications for ADHD. These medications work by increasing the levels of certain chemicals in the brain that help regulate behavior and attention.

Non-stimulant medications, such as atomoxetine, guanfacine, and clonidine, may also be used to treat ADHD. These medications work differently than stimulants and may be used when stimulants are not effective or cause unacceptable side effects.


Psychotherapy, including cognitive-behavioral therapy (CBT) and family therapy, can be effective in managing ADHD symptoms. CBT can help individuals with ADHD learn to manage their symptoms, cope with the disorder, improve their self-esteem, and develop social skills.

Family therapy can help families better understand ADHD and learn to communicate more effectively, reduce conflicts, and improve the home environment. It can also provide parents with strategies to manage their child’s behavior.

Education & Training

Education and training can be an important part of treatment for ADHD. This can involve educating the individual and their family about ADHD, its causes, its effects, and its management. It can also involve training in specific skills, such as organizational skills, time management skills, and social skills.

For children with ADHD, special education services may be beneficial. These services can provide accommodations and modifications to the learning environment to help the child succeed acadically.

Living with ADHD

Living with ADHD can be challenging, but with the right support and treatment, individuals with ADHD can lead successful and fulfilling lives. It’s important for individuals with ADHD and their families to remember that ADHD is not a reflection of an individual’s intelligence or capabilities.

With proper treatment, individuals with ADHD can manage their symptoms and achieve their goals. It’s also important to remember that individuals with ADHD often have strengths, such as creativity, energy, and the ability to think outside the box, that can be harnessed to their advantage.

Support & Resources

There are many resources available for individuals with ADHD and their families. These include support groups, educational materials, and professional organizations. Support groups can provide a safe space to share experiences, learn from others, and feel understood.

Educational materials can provide valuable information about ADHD and its management. Professional organizations, such as the American Psychiatric Association and the National Institute of Mental Health, offer resources and information about ADHD.


ADHD is a complex disorder that requires a comprehensive understanding for effective management. By understanding the nature of the disorder, its causes, its symptoms, and its treatment, individuals with ADHD and their families can better navigate the challenges of the disorder and harness its potential benefits.

While ADHD can present challenges, it’s important to remember that with the right support and treatment, individuals with ADHD can lead successful and fulfilling lives. The key is to understand the disorder, seek appropriate treatment, and focus on strengths and abilities rather than limitations.


What is ADHD?

ADHD, or Attention-Deficit/Hyperactivity Disorder, is a neurodevelopmental disorder characterized by a persistent pattern of inattention, hyperactivity, and/or impulsivity that interferes with functioning or development. It can manifest in three types: Inattentive, Hyperactive-Impulsive, or Combined.

What causes ADHD?

The exact cause of ADHD is not known, but it’s believed to involve a combination of genetic, environmental, and neurological factors. Family studies suggest a genetic component, as ADHD often runs in families. Additionally, factors like premature birth, low birth weight, and exposure to environmental toxins such as lead might increase the risk. Brain imaging studies have also shown differences in the size and activity of certain brain structures in individuals with ADHD.

How is ADHD diagnosed?

ADHD is diagnosed through a comprehensive evaluation that typically involves clinical interviews, behavioral observations, and rating scales. Information is often gathered from multiple sources, including parents, teachers, and the individual. To be diagnosed with ADHD, symptoms must be chronic, impair functioning in more than one setting (like home and school), and not be better explained by another mental disorder.

Are there effective treatments for ADHD?

Yes, there are effective treatments for ADHD. The most commonly prescribed treatments are stimulant medications, which have been shown to help reduce symptoms in many individuals. Non-stimulant medications are also available. In addition to medication, behavioral therapy, psychoeducation, and skills training can be beneficial. The best treatment often involves a combination of these approaches tailored to the individual’s needs.

Is ADHD just a childhood disorder?

While ADHD is often diagnosed in childhood, its symptoms can persist into adolescence and adulthood. In fact, many adults with ADHD were never diagnosed as children. Adult ADHD can impact various life areas, including work, relationships, and daily responsibilities. Treatment can be effective for adults as well, though it might differ from childhood interventions.