Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental mental health condition marked by hyperactive, impulsive, and inattentive behaviors. It often starts in childhood and can persist into one’s adult years.

An ADHD diagnosis is based on reported signs, symptoms, behavior, and history rather than any single test. ADHD symptoms can vary depending on the exact type and severity of the condition.

The hallmark signs of ADHD are inattention, hyperactivity, and impulsivity. For some people with ADHD, only one of these behaviors is the primary problem, but for others it’s a combination.

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 at work, at school, and at home.

ADHD is one of the most common neurodevelopmental disorders in children and is usually first diagnosed in childhood, according to the Centers for Disease Control and Prevention (CDC). In many cases, it lasts into adulthood, though how it presents — meaning the specific signs and symptoms — may change with age.

According to the CDC and National Institute of Mental Health (NIMH), children who are hyperactive may:

• Talk excessively
• Fidget and squirm
• Be in constant motion
• Have significant trouble sitting quietly or still
• Run, jump, or climb around constantly

Children who experience impulsivity may:

• Be impatient
• Have difficulty taking turns or waiting for their turn
• Frequently interrupt others
• Act or speak without thinking

Children who experience inattention may:

• Be easily distracted or become easily bored
• Have trouble focusing
• Have problems completing tasks or activities
• Daydream frequently
• Struggle with following instructions
• Switch from one activity to another frequently
• Be forgetful
• Have difficulty processing information quickly

In preschool-age children, the most common symptom of ADHD is hyperactivity-impulsivity, say NIMH experts.

In adults, according to Mayo Clinic experts, ADHD symptoms may take the form of:

• Impulsiveness
• Lack of organization and difficulty prioritizing tasks
• Difficulty focusing and following through on things
• Poor time management and planning skills
• Restlessness
• Frequent mood swings
• Difficulty coping with stress

There's no single test to diagnose ADHD, say CDC experts. Instead, doctors must assess the patient’s behavior, medical history, and environment before making a diagnosis of ADHD.

To receive a diagnosis of ADHD, children and adults must meet the criteria laid out in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5).

Children who are age 16 or younger must have six or more signs of the disorder for at least six months to a degree that's inconsistent with their developmental level, according to the CDC. Older adolescents and adults (age 17 and older) must exhibit five or more symptoms to receive the diagnosis.

ADHD symptoms include the following, say CDC experts.

Inattention

• Lack of attention to details, or careless mistakes
• Trouble maintaining attention to tasks or play activities
• Appears not to listen when spoken to directly
• Struggles to follow-through on instructions
• Difficulty completing school assignments, chores, or work
• Difficulty organizing tasks and activities
• Avoidance and reluctance to do tasks that require sustained mental effort, such as homework
• Misplaces things that are necessary for certain tasks and activities
• Easily distracted by irrelevant information and other extraneous stimuli
• Forgetful in daily activities

Hyperactivity and Impulsivity

• Fidgets or squirms in their seat
• Struggles to sit still or remain seated when it’s expected
• Runs or climbs in situations when it’s not appropriate (this may manifest as restlessness in teens or adults)
• Often unable to play quietly
• Is frequently “on the go” or acts like they’re “driven by a motor”
• Talks excessively
• Interrupts or blurts out an answer before a question has been fully asked
• Trouble waiting their turn
• Intrudes on others (In children, this could mean interrupting others' games. In adults this may involve intruding on conversations.)

For an ADHD diagnosis, these symptoms must occur in two or more settings (such as the home, school, or work), and must clearly interfere with the person's social life, schoolwork, or job. In addition, several ADHD symptoms must have been present before age 12.

Subtypes of ADHD

There are three kinds of presentations of ADHD, determined by the types of symptoms that occur.

• Predominantly inattentive presentation Mostly symptoms of inattention, and few to no symptoms of hyperactivity-impulsivity, have been present for the past six months.
• Predominantly hyperactive-impulsive presentation Mostly symptoms of hyperactivity-impulsivity, and few to no symptoms of inattention, have been present for the past six months.
• Combined presentation. Enough symptoms to meet both inattention and hyperactivity-impulsivity criteria have been present for the past six months.

An ADHD diagnosis often involves several steps. The doctor may perform a full medical exam and conduct interviews with family members or a child’s teachers to gather a personal history.

Once you or your child receives a diagnosis, you can begin proper treatment to manage ADHD symptoms.

Related Conditions

Importantly, more than two-thirds of individuals with ADHD have at least one additional coexisting condition, according to Children and Adults With Attention-Deficit/Hyperactivity Disorder (CHADD).

In children, it’s particularly important to distinguish between ADHD and other conditions that have similar signs and symptoms, or commonly occur with ADHD. These conditions or behaviors include disruptive behavior disorders like oppositional defiant disorder, learning disorders like dyslexia, medical conditions that interfere with sleep, anxiety, depression, and difficult peer relationships, say CDC experts.

In some children, signs of ADHD are noticeable as early as age 2 or 3. But diagnosing the disorder in very young children can be difficult, since developmental problems such as language delays can sometimes be mistaken for ADHD. Additionally, it can be hard to differentiate the signs of ADHD from the regular impulsivity and lack of motor control in active toddlers.

Diagnoses can be made by pediatricians or mental health professionals, though children of preschool age or younger are more likely to require an evaluation by a specialist (such as a psychologist, psychiatrist, or developmental pediatrician) to get an accurate diagnosis.

The DSM-5 now requires that each diagnosis include an assessment of the severity of the condition, whether it’s mild, moderate, or severe, because severity can change over the course of a lifetime, according to CHADD.

Diagnosing ADHD in adults poses its own challenges. While some adults may seek treatment if they suspect they have ADHD symptoms that affect their personal and professional life, some adults not previously diagnosed with ADHD may think their struggles are just a reflection of how they are as a person.

Since ADHD onset occurs in early childhood, many adults may regard their symptoms as normal and not a condition that could benefit from treatment requiring diagnosis, according to research published in The Primary Care Companion to the Journal of Clinical Psychiatry.

Statistics show that the number of children with ADHD is on the rise, but experts aren't exactly sure why.

Between the years 1997 and 2016, the percentage of children and adolescents ages 4 to 17 diagnosed with ADHD increased from 6.1 percent to 10.2 percent, according to a study published in August 2018 in JAMA Network Open.

Some experts are concerned that the disorder is being overdiagnosed because of societal pressure to treat certain behaviors, and because of increasing performance demands in schools. Others believe that ADHD is simply becoming more widely known, and that with increased awareness, more children are getting the treatment they really need.