IntroductionSummary and Conclusions
ADHD in ChildhoodAbout the Author
ADHD in AdulthoodReferences
Obstacles to Diagnosing ADHD in Adults 

Introduction

Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common mental disorders of childhood, and its impact on the child, his/her parents, and society needs no retelling. For many years, ADHD was considered a childhood disorder which remitted after puberty. However, primarily as a result of major, systematic follow-up studies whose findings were reported during the 1980s and 1990s, it is now clear that the disorder often persists into late adolescence and adulthood.

During the past 10 years, "adult ADHD" has attracted considerable attention, both professional and public. Numerous articles have appeared in prestigious psychiatric journals and in major psychiatry textbooks; specialty clinics for the diagnosis and treatment of adult ADHD have opened throughout the United States; scales for the assessment of adult ADHD have been developed by well known research groups; adult ADHD support groups and associations have been formed; web sites have been posted; popular books have been published; and newspaper and magazine articles have been plentiful.

Although there is no doubt that adult ADHD exists (i.e., that childhood ADHD persists into adulthood in a proportion of children with the syndrome), the prevalence of the adult disorder has been disputed, partly because few prospective studies have followed children with ADHD into adulthood. Long-term follow-up studies are labor-intensive, expensive, and, by definition, time-consuming. In the overwhelming majority of cases, when a diagnosis of ADHD is made in adults, it is based on adults presenting with symptoms, rather than children who have been treated for ADHD all their lives, and are now adults.

This article discusses the major obstacles in arriving at an accurate, differential diagnosis of ADHD in adults. I begin by describing the clinical portrayal of the child with ADHD.

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ADHD in Childhood

 

The "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV), which is the official system of diagnostic nomenclature in this country, defines ADHD as a persistent pattern of symptoms of inattention and/or hyperactivity-impulsivity with onset before age 7. All behavioral manifestations of the syndrome are defined by the qualifier, "often". Inattention (short attention span, distractibility, concentration difficulties) may be observed as forgetfulness, problems with organizing tasks or assignments, or a difficulty in sustaining attention. Hyperactivity is exhibited as always being "on the go," inability to remain seated, or inappropriate running or climbing. Impulsivity (impatience, acting without thinking) may be seen as blurting out answers in class, or as not being able to wait one's turn in games. The DSM-IV also requires that symptoms are present in at least two settings, e.g., home and school (cross-situationality), and that they result in clinically significant impairment [e.g., forgetting to do important tasks (inattention) may lead to problems at home, inability to remain seated (hyperactivity), to problems at school, and interrupting or intruding on others (impulsivity), to problems in social settings]. In summary, the three core symptoms that define the syndrome are developmentally inappropriate (i.e., uncharacteristic for the child's age), pervasive (i.e., cross-situational), and maladaptive (i.e., impairing).

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ADHD in Adulthood

The same three core symptoms that characterize the ADHD child are observed in the ADHD adult, although their manifestations differ somewhat.

Inattention
This is perhaps the most problematic of the ADHD symptoms since focusing attention is required for so many tasks. Inattention may also explain the consistent finding of follow-up studies that children with ADHD complete less formal schooling than their non-ADHD counterparts. Consequently, ADHD adults, compared to non-ADHD controls, are more often found in jobs that generally do not require advanced degrees, such as carpenter, plumber, and construction worker.

In addition to educational and occupational implications, concentration difficulties may pervade the ADHD adult's daily routine functioning. For example, they might frequently forget where they put their keys or parked their car; or might regularly be distracted by things like passing cars, ticking clocks, hissing coffee pots, or pets walking into the room; or might have difficulty reading a newspaper article from beginning to end without "drifting off"; or might struggle with any tasks requiring sustained attention, such as paying bills, completing tax forms, or submitting papers for dental reimbursements.

Another aspect of inattention concerns deficits in organizational skills. For example, the ADHD adult's appointment book may be so disorganized that he or she misses important appointments on a regular basis. Or they might have difficulty with time management (resulting in being late for social events), money management (causing them to sink into debt), or file management (leading to problems at work). These individuals sometimes compensate for this symptom by surrounding themselves with an organized support staff at work, or relying on their spouses to "organize their lives" and constantly remind them of important activities.

Hyperactivity
This symptom is perhaps the most apparent of the three in childhood, but tends to diminish in intensity over time. In adults with ADHD, less is observed in the form of increased gross motor activity (e.g., running and climbing), and more in the form of restlessness (foot-tapping, hand-tapping, fidgeting, squirming). They may complain of "nervousness," but careful probing reveals that they are not describing anxiety or worry, but rather an inner tension when expected to persist at relatively inactive tasks for long periods. Not surprisingly, adults with ADHD tend to avoid sedentary activities, both recreational and occupational. For example, they may have difficulty remaining seated at a restaurant, or in a church, or during meetings at work, or when listening to a lengthy conversation. This may explain why one follow-up study reported that twice as many ADHD subjects as non-ADHD comparisons were proprietors. Perhaps ADHD subjects in that study could not get themselves to settle in a 9-to-5 job because of its imposed rigidity and, instead, opted to start their own business.

The ADHD adult's pace is often very exhausting for spouses, relatives, friends, and co-workers. For example, they are always on the move as if unable to relax, and may hold several jobs to keep busy. And their incessant talking may hinder meaningful conversation. Because of their high energy output, others may describe them as "difficult to keep up with," "draining," and "always on the move".

Impulsivity
Whereas hyperactivity may reap certain benefits in adulthood (e.g., being a workaholic and earning lots of money), acting without thinking characteristically has dire consequences, e.g., quitting a job impulsively, deserting one's spouse at the drop of a hat, reflexively hitting a crying infant, and changing lanes on the highway without signaling or checking to see if anyone is there. Impulsivity may partly account for the findings that adults with ADHD, compared to non-ADHD controls, have more job instability, more marital problems, and more automobile accidents.

Another aspect of impulsivity (i.e., in addition to acting without thinking, or making regrettable, "snap" decisions) is impatience. For example, the ADHD adult may have difficulty waiting on line to purchase merchandise, or to use a bank machine, or to be seated at a restaurant, or to get into a movie theatre. The adult with ADHD may jump in on a friend when he/she is taking too long to do something, like unlock a door. Or may become frustrated when an acquaintance is taking too long to get to the point of a conversation. Although impatience is generally more benign than making quick decisions about important matters, it can be very distressing to the adult with ADHD.

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Obstacles to Diagnosing ADHD in Adults

1. Establishing Childhood ADHD

Before an adult can be diagnosed with ADHD, the childhood syndrome must be established. Interviews with the adult seeking treatment are often insufficient since retrospective diagnoses of childhood disorders are frequently unreliable. We found that 78% of children with ADHD endorsed the childhood diagnosis (i.e., retrospectively reported clinically significant childhood symptoms) at adult follow-up [chance-corrected kappa = .67]. Although this proportion may seem impressive, our subjects were severely hyperactive as children, were treated, in many cases, for years, and were regularly evaluated by multiple professionals in a child psychiatric research clinic. Most children with ADHD do not fit this mold and, as adults, are probably less likely to recall the details of their relatively less remarkable histories.

Ideally, contemporaneous information (e.g., notes written on report cards by elementary school teachers) should be obtained to substantiate retrospective diagnoses of childhood ADHD. Unfortunately, such data are often unavailable. Alternatively, a knowledgeable informant (preferably, the individual's parent) should be interviewed. Studies of children, adolescents, and adults have shown that parents are generally more accurate reporters of ADHD symptoms than subjects, themselves. However, when contemporaneous information is available, it should be given the most weight. Teachers are excellent sources, since they are unbiased (e.g., compared to parents), have a "good feel" for developmental norms (i.e., regarding symptoms of ADHD), and regularly observe the child in structured and unstructured settings with other children. Studies have also suggested that teachers are valid reporters of childhood behavior. For example, we found that children who were rated as hyperactive by teachers, but not parents, had similar young adult outcomes to children with cross-situational hyperactivity, whereas children considered hyperactive by parents, but not teachers, had outcomes no different from non-ADHD comparisons. These findings suggest that, when young adult outcome is used as an index, teacher reports are more valid than parent reports in the diagnosis of ADHD.

2. Differentiating ADHD from other Mental Disorders

The three core ADHD symptoms are shared by numerous mental disorders, most notably, the mood, anxiety, substance use, and personality disorders. For example, major depression is often characterized by psychomotor agitation and a diminished ability to think; bipolar disorder, by distractibility, an increase in goal-directed activity, and impulsivity; generalized anxiety disorder, by restlessness and difficulty concentrating; and cocaine intoxication, by hyperactivity, increased talkativeness, agitation, and impulsive acts. Regarding Axis II diagnoses, persons with borderline personality disorder, like many adults with ADHD, are often characterized by impulsive acts, inconsistent work histories, impaired social relationships, and substance abuse.

All of these disorders must be distinguished from ADHD, and the potential implications of a misdiagnosis are not trivial. Consider an individual with major depression who is incorrectly diagnosed as having ADHD. If treated with psychostimulants (the medication of choice for adult ADHD), rather than antidepressants, the person's condition may not respond, or even worsen.

Ruling out other disorders involves three things: being aware of those disorders that may simulate adult ADHD, knowing the criteria for those disorders (particularly, the symptoms that are not shared with ADHD), and carefully assessing the onset and course of the disorder under consideration. Concerning the latter point, remember that adult ADHD defines a persistent condition that originated in childhood. So if presumed ADHD symptoms follow an episodic pattern they may be associated with a disorder other than ADHD.

3. Assessing Comorbidity

In addition to determining whether other diagnoses account for ADHD symptoms, there may also be comorbid syndromes in adults who truly have had ADHD since childhood. For example, follow-up studies of children with ADHD consistently have shown that they are at risk for antisocial personality disorder, compared to non-ADHD controls. The key to distinguishing between disorders that account for ADHD symptoms, and disorders that are comorbid with ADHD, is teasing out the onset, chronicity, and developmental sequence of the syndromes. For example, if concentration difficulties and restlessness are exhibited during, but not between, episodes of major depression, then the major depression likely accounts for the symptoms. If, on the other hand, the individual states that he has been plagued by these symptoms "for as long as I can remember," but that they became more intense and frequent during the periods of depression, then the major depression is likely a comorbid disorder. In this particular example, the interviewer also would have to rule out a double depression (i.e., one or more episodes of major depression superimposed on dysthymic disorder) in the absence of adult ADHD, since dysthymic disorder also may be characterized by these symptoms. This illustration further underscores the difficulty in arriving at an accurate differential diagnosis.


4. Differentiating ADHD from General Medical Conditions

In addition to mental disorders, certain non-psychiatric medical conditions may also simulate adult ADHD. Examples include hypo- and hyper-thyroidism, diabetes, seizure disorder, and head injury. Therefore, a complete medical history (and, in some cases, a comprehensive physical examination) should be part of the diagnostic process.

5. Differentiating ADHD from Situational Factors

Environmental factors also influence the individual's mental status, and reactions to certain prolonged life stressors may be mistaken for chronic conditions. For example, someone who is embroiled in a tumultuous divorce and an intense custody battle that continue for years may experience restlessness, concentration difficulties, and even impulsivity throughout that period. When conducting the initial assessment, the interviewer must always be aware of life events that may account for the individual's symptoms. It may help to ask the respondent whether anything going on in his/her life may have contributed to the way he/she is feeling or behaving. Also, as stated above, course of symptoms must be ascertained to establish persistence.

6. Establishing Cross-Situationality and Impairment

As indicated earlier, cross-situationality (symptoms in more than one setting) and impairment are DSM-IV requirements for the diagnosis of ADHD. The impairment criterion is usually not a problem, since persons seeking help for adult ADHD symptoms usually suffer from clinically significant impairment, which is why they are coming for treatment. However, if cross-situationality is not explicitly addressed in the assessment a false positive diagnosis of ADHD can be made. For example, an individual working for an unfair, unappreciative, overly demanding employer may seek help for longstanding agitation and distractibility which are affecting his performance at work (occupational impairment). Only careful probing may reveal that these symptoms are unique to the work setting, e.g., he does not experience them at home or with friends. Most likely, the correct diagnosis in this case would be adjustment disorder, not ADHD. This example also illustrates two of the obstacles discussed above, Differentiating ADHD from other Mental Disorders (in this case, adjustment disorder), and Differentiating ADHD from Situational Factors (which, in this case, resulted in developing a mental disorder).

Failure to pay attention to the diagnostic criteria also has implications for research in the field of adult ADHD. In a recent study whose objective was to estimate the prevalence of adult ADHD in the general population, subjects were sampled from the community and administered ADHD symptom questionnaires by lay interviewers (i.e., non-clinicians). No attempt was made to assess cross-situationality or impairment. For the reasons reviewed above, this study likely overestimated the rate of adult ADHD by disregarding key requirements of the disorder.

7. Contending with Self-Diagnoses of Adult ADHD

This is perhaps the most challenging obstacle to a differential diagnosis of adult ADHD. During the past decade, the fairly extensive media coverage of adult ADHD (feature articles in major magazines, news specials on television, etc.) has educated the public considerably, regarding the clinical features of the disorder, and even the other DSM-IV requirements (impairment, etc.). Consequently, some adults (without ADHD) have identified with the symptoms, and have embraced the diagnosis almost as a solution to their longstanding problems. Then they show up at an adult ADHD clinic and present a textbook case of the disorder. The actions of these individuals are not intentionally deceptive, i.e., they truly believe that they have ADHD. And their description of even the childhood syndrome (memories which have been selectively recalled and distorted by their readings of media material) can be very convincing.

Many of the tools described above must be brought into play when individuals present themselves as "classic cases." For example, obtaining contemporaneous information (or, at the very least, an interview with a knowledgeable informant) to establish the childhood diagnosis becomes even more important, since the patient's reports of the frequency and severity of childhood symptoms may be exaggerated. The good news is that these individuals are not likely to lie, since their intention is not to misled the interviewer. Therefore, with careful probing, the diagnostician will be able to differentiate between adult ADHD and other mental disorders, comorbid syndromes, etc.

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Summary and Conclusions

Stedman's Medical Dictionary defines "differential diagnosis" as "the determination of which of two or more diseases with similar symptoms is the one from which the patient is suffering" (23rd edition, p. 386). Stated differently, it is the process of identifying the correct diagnosis. Disorders often share common symptoms, and ADHD is no exception. For example, the many manifestations of inattention (poor memory, concentration difficulties, disorganized behavior, distractibility, etc.) are ubiquitous in psychiatry, and are observed in child, adolescent, and adult disorders. Inattention, by itself, does not inform diagnosis, and the same can be said for impulsivity and hyperactivity. But even if all three of these symptoms are observed in concert, other factors must be considered in arriving at an accurate differential diagnosis. A careful assessment by a skillful and knowledgeable clinician is needed to integrate all relevant material (onsets, offsets, developmental progression of symptoms, other symptomatology, life events, etiology, severity, etc.). As we have seen, the evaluator must establish childhood ADHD, determine whether adult symptoms are better explained by other mental and physical disorders, assess comorbidity, consider the importance of situational factors, and appraise cross-situationality and functional impact. It is highly unlikely that a simple checklist of symptoms can make these critical distinctions, nor is the self-referred, self-diagnosed individual capable of making these clinical judgments. An incorrect diagnosis of adult ADHD may lead to inappropriate, and even harmful treatment, whereas an accurate differential diagnosis is likely to benefit the patient and perhaps advance our knowledge of this chronic, often debilitating syndrome.

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References

1. Barkley, R.A. (1998). Attention-Deficit Hyperactivity Disorder. Second Edition. New York, NY: The Guilford Press.

2. Mannuzza, S., Klein, R.G., Klein, D.F., Bessler, A., & Shrout, P. (2002). Accuracy of adult recall of childhood attention deficit hyperactivity disorder. American Journal of Psychiatry, 159, 1882-1888.

3. Mannuzza, S., Klein, R.G., & Moulton, J.L., III (2003). Persistence of attention deficit hyperactivity disorder into adulthood. Journal of Attention Disorders, 7, 93-100.

4. Weiss, M., Hechtman, L.T., & Weiss, G. (1999). ADHD in Adulthood. Baltimore, MD: The John Hopkins University Press.

5. Wender, P.H. (1995). Attention-Deficit Hyperactivity Disorder in Adults. New York, NY: Oxford University Press.