Understanding Adult ADHD

By Heidi Bernhardt, RN

Access What You Need to Know About ADHD, a summary of adolescent and adult ADHD and Ce que vous devez savoir à propos du TDAH.

Adult ADHD is a neurodevelopmental disorder that can also be categorized as a mental health condition.

Incident Rates

It was formerly believed that children outgrew their ADHD symptoms in adolescence but we now know that over sixty percent of adults maintain some of their impairing core symptoms into adulthood. Some adults with Attention-Deficit Hyperactivity Disorder (ADHD) may have been diagnosed with ADHD in childhood and some may have received treatment, however many adults are unaware that their difficulties are caused by ADHD until diagnosed. The accepted conservative prevalence rate of adult ADHD is four percent. ADHD is not strictly a North American phenomenon, but a disorder that is recognized worldwide.


Symptoms include difficulty with regulating attention (being unable to focus for any length of time, hyper-focusing with the inability to break focus, and difficulty with prioritizing focus) to a level of impairment and possibly, but not necessarily, hyperactivity and impulsivity. As in childhood, there are three subtypes of ADHD that are determined based on the type of symptoms displayed, including: primarily inattentive (formerly known as ADD), combined (all three symptoms), and primarily hyperactive (extremely rare). Many of the symptoms of the primarily inattentive subtype of ADHD may be internalized, making them more difficult to identify.

Some ADHD symptoms, such as outward hyperactivity, may decrease throughout the life cycle however many adults still describe a consistent feeling of internal restlessness. Some adults report that they have simply learned how to channel their restlessness into more appropriate outlets. Impulsivity may decrease in adulthood or at least change in its presentation, however, many adults with ADHD find their verbal impulsivity, impulsive reactions, and impulsive spending habits can get them into a great deal of trouble. Executive Functioning impairments such as difficulty with working memory, organization, time management, planning, and prioritizing, as well as social ills are also common in adults with ADHD.  For a complete list of symptoms access “Adult Symptoms”. 

What Causes Adult ADHD?

ADHD is a disorder with a strong genetic component. A small percentage of ADHD may be caused by drinking and smoking during pregnancy, obstetrical complications, or through later brain trauma or exposure to lead or other toxins.

Although the exact cause of ADHD is still unknown, brain imaging has identified differences in the brains of those with ADHD. For further details access: http://www.nimh.nih.gov/health/publications/attention-deficit-hyperactivity-disorder/index.shtml.  ADHD Researchers have also studied impairments in the brain chemical neurotransmitters, dopamine, norepinephrine and epinephrine, as being a contributing cause of the disorder.

Diagnostic Criteria

Although not always diagnosed in childhood, symptoms must have been evident before the age of twelve for adult ADHD to be diagnosed. ADHD does not suddenly appear in adulthood. Many adults end up being diagnosed with this disorder after their children are assessed for ADHD. While it is true that most people experience many of these symptoms from time to time, symptoms of attention dysregulation, hyperactivity and impulsivity must be at levels of impairment for a diagnosis to occur. There is a significant difference between having occasional difficulty paying attention when tired or stressed, and not being able to pay attention most of the time, no matter how much effort you extend or how important it is. Due to the recognition that the presentation of symptoms change as children get older, DSM 5  recently lowered the requirements for the diagnosis of adults and older adolescents, with five recognizable symptoms now required versus six for children. For detailed information on what is involved in a comprehensive assessment and diagnosis of adult ADHD, please access “Adult ADHD Assessment and Diagnosis”.

Gender Differences

Although we still diagnose ADHD three times more often in boys than girls, by adulthood gender incident rates become more equal. This indicates that we are still under diagnosing girls. This is most likely due to the fact that females are more often diagnosed with the primarily inattentive subtype with less hyperactivity and impulsivity. Although the hyperactivity and impulsivity alerts teachers and parents to a potential case of ADHD and an earlier diagnosis, it is the difficulty with attention regulation, seen in both common subtypes, that causes the greatest degree of academic difficulty. Many female adults with ADHD as children and adolescents remember spending most of their time in class day dreaming, being tuned out and unable to focus on learning. Women are generally diagnosed later in life.

In the past and to some extent still today, women with ADHD tend to be diagnosed with depression rather than ADHD. Sometimes this depression occurs along with their ADHD and should be dually diagnosed, but other times physicians not trained in ADHD misinterpret attention difficulties as depression rather than the primarily inattentive subtype of ADHD. Although both males and females present equally with coexisting disorders of anxiety and depression, women suffer with more psychological distress and lower self-esteem. Studies have shown that females are five times more likely than males to be diagnosed with depression and three times more likely to be treated for depression before their ADHD diagnosis. Additional coexisting disorders common in women are compulsive overeating, chronic sleep deprivation, chronic stress and fibromyalgia. Hormonal fluctuations can cause additional difficulties as ADHD symptoms increase as estrogen decreases. This also makes medication therapy more of a challenge. When untreated, males with ADHD show a higher incidence of criminality and abuse. Symptom intensity and subtype symptoms did not differ between males and females.

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