Updated February 05, 2015.

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While attention deficit hyperactivity disorder (ADHD) is generally thought to be a disorder of childhood, the majority of children with ADHD have some symptoms that persist into adulthood.  These symptoms can cause significant problems in life at work, academics, or in social settings. 

It’s been estimated that about 4.4 percent of adults aged 18 to 44 in the United States have ADHD, though this statistic widely varies.

 As with children, adults with ADHD are at an increased risk for other disorders as well, including problems with mood, anxiety, and substance abuse.

What Causes ADHD?

There’s likely to be a genetic component to ADHD, as the risk is higher in those who have a first degree relative (such as a child or parent) with ADHD.  Twin studies estimate that there is about 76 percent hereditability.  Several genes have been implicated, but these genes are thought to increase risk of ADHD rather than having a direct causal effect. 

Some of the genes implicated in ADHD are related to dopamine, a neurotransmitter closely involved with the reward pathways of the brain.  Decreased dopamine activity, as well as reduced activation of other neurotransmitters such as norepinephrine, is thought to underlie many of the symptoms of ADHD.   These neurotransmitters work within a network between the frontal cortex of the brain, the basal ganglia, and the cerebellum to help organize and focus thought and action.

Neuroimaging studies of those with ADHD show predominantly right hemispheric disruption of prefrontal cortical circuitry.

  There may be some structural changes as well, with small frontal, cerebellar, and basal gangliar volumes.  Early studies suggest that while some of these findings normalize by adulthood, cortical abnormalities (on the surface of the brain) remain. 

Clinical Symptoms of ADHD in Adults

While many children with ADHD are hyperactive, this trait seems to be less obvious in adults.  Some adults with ADHD may report feeling fidgety or restless.  However, the primary problem in adults seems to be inattention.

Inattentiveness impacts day-to-day life in the form of poor time management, forgetfulness, inability to prioritize, poor organization, and poor follow through on tasks.  Psychological tests may show more signs of executive dysfunction.  Adults may have low tolerance for frustration.  In addition, the educational difficulties, problems with self-esteem, and impaired social relationships that so often accompany ADHD may lead to a higher rate of occupational problems, criminal activity and substance abuse than among adults without ADHD. 

Symptoms of ADHD do not seem to uniformly follow a distinctive pattern through the adult lifespan.  Sometimes symptoms improve, and sometimes they worsen.  Regardless, recognizing symptoms can lead to help.

What Else Could It Be?

It’s important not to jump straight to a diagnosis of ADHD, but instead consider other possibilities.  This is especially the case if an adult suspected of having ADHD didn’t clearly show symptoms during childhood.  While sometimes additional stressors of adulthood may bring out ADHD symptoms that had gone unnoticed until later in life, the stresses of childhood are far from insignificant, and symptoms would usually be noticed.

Depression  and anxiety disorders can also impact attention and concentration, and sufferers may be indecisive.  Mania can also cause impulsivity and distractibility.  Substance use can lead to poor attention, distractibility or hyperactivity.  Certain dementias can also do this, especially later in life.  Because the risk of some of these disorders such as depression or anxiety goes up if ADHD is present, it can be difficult to determine if someone has ADHD, a different disorder, or both.

If someone suspects they may have ADHD, it is best to be evaluated by a medical professional who can first confirm the diagnosis and investigate for the presence of other or additional disorders.  That professional may then be able to offer appropriate treatments for whatever problems are present.

<sub>Source:

Oscar Bukstein, Adult attention deficit hyperactivity disorder in adults: Epidemiology, pathogenesis, clinical features, course, assessment, and diagnosis Up-to Date, Updated Aug 1, 2014. Accessed December 29, 2014</sub>