Epidemiology, Impairments, and Differential Diagnosis in Adult ADHD: Introduction

Lenard A. Adler, MD

CNS Spectr
. 2008;13:8(Suppl 12):4-5


An expert panel review of clinical challenges in primary care and psychiatry


Funding for this activity has been provided by an educational grant from Shire Pharmaceuticals Inc.


Accreditation Statement

This activity has been planned and implemented in accordance with the Essentials and Standards of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the Mount Sinai School of Medicine and MBL Communications, Inc. The Mount Sinai School of Medicine is accredited by the ACCME to provide continuing medical education for physicians. 

Credit Designation

The Mount Sinai School of Medicine designates this educational activity for a maximum of 2 AMA PRA Category 1 Credit(s)TM. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Faculty Disclosure Policy Statement

It is the policy of the Mount Sinai School of Medicine to ensure objectivity, balance, independence, transparency, and scientific rigor in all CME-sponsored educational activities. All faculty participating in the planning or implementation of a sponsored activity are expected to disclose to the audience any relevant financial relationships and to assist in resolving any conflict of interest that may arise from the relationship. Presenters must also make a meaningful disclosure to the audience of their discussions of unlabeled or unapproved drugs or devices. This information will be available as part of the course material.

This activity has been peer reviewed and approved by Eric Hollander, MD, Chair and Professor of Psychiatry at the Mount Sinai School of Medicine. Review Date: July 22, 2008.

Statement of Need and Purpose

Although attention-deficit/hyperactivity disorder (ADHD) has traditionally been considered a pediatric disorder, up to 65% of children diagnosed with this disorder continue to display behavioral problems and symptoms of the disorder into their adult lives. ADHD has a deleterious impact upon the daily functioning of these adults, who often demonstrate functional impairments in multiple domains, including educational performance, occupation, and relationships. Accurate diagnosis of ADHD in adults is challenging and requires careful consideration of other psychiatric and medical disorders. The majority of adults with ADHD exhibit at least one co-morbid psychiatric disorder, which may confound a proper ADHD diagnosis. Although adult ADHD is a substantial source of morbidity in both psychiatric and primary care settings, only 25% of adults with this disorder had been diagnosed in childhood or adolescence. Among patients who had not received a prior diagnosis, more than half had complained about ADHD symptoms to other healthcare professionals, without being diagnosed. Recognition and treatment of adult ADHD is often based on upwardly extended models of child and adolescent care. However, differing patterns of co-morbidity and symptom heterogeneity in adults pose new conceptual, diagnostic, and treatment challenges. Although several organizations have issued practice guidelines for the assessment of adults with ADHD, there remains confusion and a continued need to determine best practices with regard to these patients. The expert opinions of clinical and research thought leaders in the field provide insight relevant to clinicians faced with the task of recognizing impairment and diagnosing adult ADHD.

Target Audience

This activity is designed to meet the educational needs of primary care physicians and psychiatrists.

Learning Objectives

• Review the epidemiology of attention-deficit/hyperactivity disorder (ADHD), including prevalence, persistence, and co-morbid tendencies.
• Explain the common impairments associated with adult ADHD and how to incorporate assessment of impairment levels into the diagnostic process. 
• Discuss the differential diagnosis and psychiatric co-morbidities that require consideration in the assessment of adult ADHD.

Faculty Disclosures

Lenard A. Adler, MD, is a consultant to and on the advisory boards of Abbott, Cephalon, Cortex, Eli Lilly, Novartis, Ortho-McNeil, Janssen, Johnson and Johnson, Merck, New River, Organon, Pfizer, Psychogenics, sanofi-aventis, and Shire; is on the speaker’s bureaus of Eli Lilly and Shire; and receives grant/research support from Abbott, Bristol-Myers Squibb, Cephalon, Cortex, Eli Lilly, Janssen, Johnson and Johnson, Merck, National Institute of Drug Abuse, New River, Novartis, Ortho-McNeil, Pfizer, and Shire.

Acknowledgment of Commercial Support

Funding for this activity has been provided by an educational grant from Shire Pharmaceuticals Inc.

Peer Reviewer

Eric Hollander, MD, reports no affiliation with or financial interest in any organization that may pose a conflict of interest. 

To Receive Credit for this Activity

Read this Expert Roundtable Supplement, reflect on the information presented, and complete the CME posttest and evaluation. To obtain credit, you should score 70% or better. Early submission of this posttest is encouraged. Please submit this posttest by August 1, 2010 to be eligible for credit.

Release date: August 1, 2008
Termination date: August 31, 2010

The estimated time to complete this activity is 2 hours.

A related audio CME PsychCastTM will also be available online in September 2008 at: cmepsychcast.mblcommunications.com and via iTunes.


Attention-deficit/hyperactivity disorder (ADHD) is commonly thought to be a pediatric disorder whose symptoms attenuate or disappear in adulthood. In fact, ~4% of adults in the United States have ADHD, and many of these adults are unaware that they have the disorder. Because symptoms of ADHD manifest differently in adults and children, physicians who are familiar with childhood ADHD have difficulty identifying the disorder in adults. Adults with ADHD themselves may be poor informants about their symptoms and impairments. A high prevalence of mood and other co-morbid disorders in adults with ADHD can also complicate diagnosis and treatment. Adults with ADHD experience high rates of anxiety disorders, mood disorders, substance use disorders, and impulse disorders. Adult ADHD is related to impairments in executive functioning and adaptive functioning; these patients have unique deficits related to their roles as parents, caregivers, and employees. Physicians should use impairments to guide treatment design. Early identification and treatment of ADHD can alter the developmental course of co-morbid disorders. Unfortunately, metrics for impairment in adult ADHD are still in their infancy.

This Expert Roundtable Supplement represents part 1 of a 3-part supplement series on adult ADHD led by Lenard A. Adler, MD. In this activity, Thomas J. Spencer, MD, reviews the epidemiology of adult ADHD in the US and around the world; Mark A. Stein, PhD, reviews data on the impairments resulting from adult ADHD; and Jeffrey H. Newcorn, MD, discusses the differential diagnosis of adult ADHD and common co-morbidities.

Faculty and Disclosures

Dr. Adler is associate professor of psychiatry and child and adolescent psychiatry, and director of the Adult ADHD Program, both at the New York University Langone School of Medicine.

Disclosures: Dr. Adler is a consultant to and on the advisory boards of Abbott, Cephalon, Cortex, Eli Lilly, Novartis, Ortho-McNeil, Janssen, Johnson and Johnson, Merck, New River, Organon, Pfizer, Psychogenics, sanofi-aventis, and Shire; is on the speaker’s bureaus of Eli Lilly and Shire; and receives grant/research support from Abbott, Bristol-Myers Squibb, Cephalon, Cortex, Eli Lilly, Janssen, Johnson and Johnson, Merck, National Institute of Drug Abuse, New River, Novartis, Ortho-McNeil, Pfizer, and Shire.


In the mid-1970s, attention-deficit/hyperactivity disorder (ADHD) was still believed to be a childhood disorder that disappeared with the onset of adolescence. At this time, Wender1 studied a cohort of adults presenting with ADHD-like symptoms, all of whom had been diagnosed with ADHD in childhood. Wender prescribed psychostimulants, which successfully produced a response in the adults, thus fostering research into adult ADHD. Of his experience, Wender said:   

ADHD is probably the most common chronic undiagnosed psychiatric disorder in adults. It is characterized by inattention and distractibility, restlessness, labile mood, quick temper, overactivity, disorganization, and impulsivity. It is always preceded by a childhood diagnosis, a disorder that is rarely inquired about and usually overlooked.1   

Wender’s predictions were later corroborated (although labile mood and quick temper are not defined as core features in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-Text Revision [DSM-IV-TR]).2 The National Co-morbidity Survey Replication has demonstrated that the prevalence of ADHD in adults in the United States is ~4.4%, but that only 11% of these patients receive treatment.3 Self-report data from Barkley and colleagues4 showed a 4.7% ADHD prevalence rate among adults applying for driver’s licenses. Four percent of adult college students met DSM-IV5 criteria for ADHD.6 Though Wender had specified that adult ADHD is always preceded by a childhood diagnosis, for many individuals the condition is overlooked during childhood and the diagnosis is never made. However, it is true that all cases of full adult DSM-IV ADHD are preceded by childhood onset of significant symptoms.

ADHD has been described over time in such terms as “minimal brain dysfunction” and “minimal brain damage” (Slide 1). ADHD was originally described in 1902 by Still,7 whose clinical descriptions of children closely resemble today’s diagnostic criteria for ADHD. The first treatment for this disorder was a racemic mixture of amphetamine in 1937. A full adult diagnosis of active ADHD would not be included in the DSM-III-R8 until 1987.

Diagnostic and Statistical Manual of Mental Disorders Criteria

There are five major criteria for adult ADHD in the DSM-IV (Slide 2).5 The first criterion is significant presence of six out of nine inattentive symptoms and/or hyperactive/impulsive symptoms over the past 6 months. Patients with six of nine inattentive symptoms have the inattentive subtype of ADHD. Patients with six of nine of the hyperactive/impulsive symptoms have the hyperactive/impulsive subtype of ADHD. Patients with six of nine of both symptom types have the combined subtype.

The second criterion is age of onset. Patients must have onset of at least some symptoms before 7 years of age. This is best obtained by taking a longitudinal history and obtaining collaterals (information from surviving parents or older siblings or old report cards, when available). Third, some impairment from the symptoms must be present in two or more settings, ie, school, work, or in social settings. It is important to note that the impairment can be relative (ie, underperformance relative to the expected capabilities of the individual). Fourth, the impairment must be significant and fall in the realm of social, academic, or occupational deficit. Finally, symptoms should not be better accounted for by another mental health disorder. If the symptoms of ADHD only appear during the active phase of another mental health disorder, they should be coded for that disorder and not ADHD.

Longitudinal history is critical for making the diagnosis of ADHD. Although the disorder is highly co-morbid (ie, 50% to 75% in adults),3 the onset of ADHD symptoms and those of other disorders will often distinguish themselves over an extended period of time—with the ADHD symptoms generally preceding those of other disorders.

Symptoms Manifestation in Adulthood

Symptoms change over the course of a patient’s lifetime. The symptoms noted in the DSM-IV are specific to childhood. Clinicians are therefore left to interpret how those symptoms will manifest in adults. Childhood inattention symptoms, such as difficulty sustaining attention, not listening, not following through, not organizing, losing things, and easy distraction, more often present as poor time management, trouble initiating and completing tasks, trouble with multitasking, procrastination, and avoiding activities that demand attention in adults (Slide 3).9 Many adults do not recognize that inattention can significantly impact their lives. Adults cope with their symptoms and tend to adapt to them by self-selecting active lifestyles and using support staff. It is important to observe how adults deal with their symptoms. Adults have a higher cognitive load than children, so it is not surprising that the inattentive symptoms become more problematic as one reaches adulthood.

Hyperactivity symptoms also change over a patient’s lifetime. The childhood symptoms are squirming and fidgeting, not staying seated, running about, climbing, not playing/working quietly, being “on the go” or “motor-driven,” or talking excessively. This aimless restlessness in childhood migrates to purposeful restlessness in adulthood. Adults often cope with this sense of restlessness by working two jobs, working long hours, or selecting active jobs. Family tension is often a consequence of this constant activity. There may be consequences to the individual’s excess activity; for example, long hours at work may compromise time spent with family. These are common complaints. Adults with ADHD tend to avoid low-activity situations, such as circumstances in which they would have to sit still, or they might plan breaks for such circumstances. The frank hyperactivity is often felt rather than manifested because obvious manifestations, such as constantly moving about in the workplace, can be stigmatizing.

Impairments in Adult ADHD

The consequences of ADHD symptoms are significant, and the impairments are notable. Barkley and colleagues10 compared the adult adaptive outcomes of nearly 140 patients with and without ADHD, following subjects for 13 years. They found that adults with untreated ADHD are four times as likely to contract a sexually transmitted disease and three times as likely to be unemployed. In a population survey of 500 ADHD adults and 501 gender- and age-matched adults without ADHD, Biederman and colleagues11 found that adults with ADHD were twice as likely to be divorced, and twice as likely to have been arrested. Adults with untreated ADHD are 78% more likely to be addicted to tobacco and are less likely to quit a tobacco habit.


1. Wender PH. Attention-Deficit Hyperactivity Disorder in Adults. New York, NY: Oxford University Press; 1995.
2. Diagnostic and Statistical Manual of Mental Disorders. 4th ed text rev. Washington, DC: American Psychiatric Association; 2000.
3. Kessler RC, Adler L, Barkley R, et al. The prevalence and correlates of adult ADHD in the United States: results from the National Comorbidity Survey Replication. Am J Psychiatry. 2006;163(4):716-723.
4. Barkley RA, Murphy KR, Kwasnik D. Motor vehicle driving competencies and risks in teens and young adults with attention deficit hyperactivity disorder. Pediatrics. 1996;98(6 Pt 1):1089-1095.
5. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 1994.
6. Heiligenstein E, Conyers LM, Berns AR, Miller MA. Preliminary normative data on DSM-IV attention deficit hyperactivity disorder in college students. J Am Coll Health.1998;46(4):185-188.
7. Still GF. Some abnormal psychical conditions in children. Lancet. 1902;1:1008-1012,1077-1082,1163-1168.
8. Diagnostic and Statistical Manual of Mental Disorders. 3rd ed rev. Washington, DC: American Psychiatric Association; 1987.
9. Weiss M, Trokenberg L, Hechtman L, Weiss G. ADHD in Adulthood: A Guide to Current Theory, Diagnosis and Treatment. Baltimore, MD: The Johns Hopkins University Press; 1999.
10. Barkley RA, Fischer M, Smallish L, Fletcher K. Young adult outcome of hyperactive children: adaptive functioning in major life activities. J Am Acad Child Adolesc Psychiatry. 2006;45(2):192-202.
11. Biederman J, Faraone SV, Spencer TJ, Mick E, Monuteaux MC, Aleardi M. Functional impairments in adults with self-reports of diagnosed ADHD: A controlled study of 1001 adults in the community. J Clin Psychiatry. 2006;67:524-540.