FROM THE CLINICAL KNOWLEDGE CENTER
Recognizing ADHD in Our Adult Patients

by Francois Theberge, MD

Introduction

Since the first descriptions of childhood ADHD in the medical literature, ADHD has become the most commonly diagnosed neurodevelopmental disorder in children and adolescents.(1) ADHD can significantly impact children in the social, emotional, and academic spheres of life. There is a higher prevalence of problems with self-esteem, peer relationships, delinquency,(2) and substance abuse(3-4) among children with ADHD than their non-affected peers.

Growing evidence suggests that childhood ADHD persists throughout adulthood;(5) between 30% to 66% of children with ADHD will carry a significant burden of symptoms into adulthood.(6) ADHD may interfere with the social and occupational life of adults and is associated with behaviors that place them at increased medical risk. Moreover, as the individual learns to develop coping strategies, the manifestations of the disease can be markedly modified. This complicates the task of accurately diagnosing adult ADHD.

A PubMed search on the term ADHD shows that the number of publications has increased 139% every 5 years, since 1995, whereas the media coverage of ADHD has grown even more rapidly. However, all this information about symptoms, signs, and treatment offers scant guidance about who and when to treat.

Definition and evolution of ADHD

ADHD was originally considered a disorder limited to childhood, with a pronounced emphasis on symptoms of hyperactivity. Over time, it became increasingly recognized that attentional deficits were not only important, but also persistent and disabling.

There are notable clinical similarities between childhood and adult ADHD. Both exhibit similar molecular, genetic, and neuroimaging findings. Adults with ADHD usually respond to the same medications used to treat childhood ADHD.(7-8) Patterns of psychiatric comorbidity are also quite similar between the two groups. The consensus is that adult ADHD is a continuation of childhood ADHD. However, as the brain develops to its adult state, the individual develops environmental coping strategies and the manifestations of the disease can undergo several changes. Fifty percent to 80% of adults with ADHD that had ADHD in childhood no longer meet full DSM-IV criteria. This can make the accurate diagnosis of ADHD in adults a challenge.

ADHD is a heterogeneous group of neurobiologic dysfunctions with an estimated heritability of 76%;(9) that is, genetic transmission accounts for 76% of the etiology. Interestingly, studies point to impaired transport of brain norepinephrine and dopamine that results in decreased availability at the receptor site. PET scan data in adults with ADHD have shown that methylphenidate inhibits the action of dopamine transporters in a dose-dependent manner.(10) When administered at therapeutic doses, methylphenidate's peak behavioral effects correlate with both a time-to-peak uptake of dopamine and a >50% occupation of dopamine transporters. Positron emission tomography (PET) scans of the brains of adults with ADHD have shown that when engaged in decision making, their neural circuits are different than in the brains of control subjects.(11-12) Functional magnetic resonance imaging (fMRI) studies of adults with ADHD indicate involvement of the frontal lobes, basal ganglia and corpus callosum(13) - areas of the brain responsible of executive functions. These functions include impulse control, organization, planning, self-monitoring capacity, decision-making, and working memory. Consequently, ADHD hinders the capacity of the affected individual to regulate attention, impulsivity, emotional expression, motor behavior, and pertinent application of higher-order executive functions.

The behavioral translation of these findings is an individual who is able to concentrate, but unreliably. When engaged in preferred activities, most people with ADHD can focus very well, but may experience difficulties in maintaining concentration if they are bored or distracted by more exciting internal or external stimuli. Some individuals with ADHD may also have difficulty switching from a task in which they are absorbed to refocus their attention elsewhere.

Impact of ADHD

These attentional and control deficits often lead to social and occupational impairments, as well as a higher tendency toward medically high-risk behavior. Yong adults with ADHD tend to use less contraception, have more sexual partners and have a higher prevalence of sexually transmitted diseases than their neurotypical peers of the same age group.(14) Consumption of alcohol, cigarettes, and recreational drugs is also reported to be more prevalent in adults with ADHD (15-16). Adults with ADHD have significantly more difficulty in keeping jobs, and income studies show that on average, they earn less, ($8,900 to $15,400 less) and are more often unemployed than the general population.(17)

	ADHD	Control
Graduation rate (%) -- High school -- College	83 19	93 25
a Job stability	5.4	3.4
Employed at time of survey	52	72
b Feeling of inadequacy	24	9

a. Expressed in number of jobs held in the last 10 years
b. 24% of the adults with ADHD reported 11 days per month where they were not "fully engaged" both physically and emotionally due to ADHD symptoms, as compared to only 9% of those adults without ADHD

Without diagnosis and treatment, adults with ADHD face a constant struggle in realizing their potential and are exposed to high-risk behavior affecting several aspects of their lives.

This article is an excerpt from a multipart monograph on adult ADHD. To access the remaining portions covering treatment, psychiatric comorbidity, and conclusions, please visit the neuroscienceCME.com ADHD Clinical Knowledge Center by clicking here. (Requires free account activation at neuroscienceCME.com)

Do you have feedback for the author? Click here to send us an email.


References