Kasra Behizad is a first-year medical student at the Keck School of Medicine of USC with a concentration in primary care and community medicine. His research interests include designing community health empowerment programs and investigating the role of spirituality/religion in the healing process.
Attention deficit hyperactivity disorder (ADHD) is an increasingly prevalent neurodevelopmental disorder that causes significant individual and societal burden. A dramatic rise in the number of ADHD diagnoses in children and adults, in addition to an associated rise in prescriptions for ADHD medication suggests overdiagnosis and overtreatment. The recent publication of DSM-5 brings with it an added potential for overdiagnosis. Current diagnostic standards rely on qualitative assessment, resulting in high variability. This paper reviews other diagnostic modalities that reduce the risk of overdiagnosis and underdiagnosis.
Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder in children and adolescents (Wolraich et al. 1007-1022), and often continues into adulthood (Barkley et al. 279-289). Individuals with the disorder are characterized by a persistent and debilitating combination of inattentiveness, impulsivity, and/or hyperactivity. The Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5) classifies individuals with ADHD into one of three categories: 1) predominantly inattentive, 2) predominantly hyperactive/impulsive, or 3) combined (American Psychiatric Association and DSM-5 Task Force). Research studies demonstrate a strong genetic underpinning for the disorder (Simon et al. 204-211), as well as neurological abnormalities in brain-wave patterns (Barry, Clarke, and Johnstone 171-183) and brain size (Castellanos et al. 1740-1748). When compared to their peers, children with ADHD experience reduced academic performance, while adults with ADHD experience reduced occupational attainment (Frazier et al. 49-65). Adult sufferers are also at greater risk of unemployment (Kessler et al. 716-723). Individuals with ADHD are also more likely to experience social rejection (Kessler et al. 716-723), incarceration (Klein et al. 1295-1303), physical injury (Merrill et al. 20-26), substance abuse (Klein et al. 1295-1303), and traffic accidents (Merrill et al. 20-26). Altogether, these functional impairments highlight the deleterious effect of ADHD on individuals and the public.
The prevalence of ADHD in children and adults has increased over the past three decades. After the publication of DSM-IV in 1992, the rate of diagnosed childhood ADHD more than tripled from 3% (Goldman et al. 1100-1107) to 9.5% in 2007 (Visser et al. 1439). Relatedly, the percentage of American children taking stimulant medications doubled from 2.4% to 4.8% between 1996 (Olfson et al. 514-521) and 2007 (Visser et al. 1439). This may be due in part to a change in the diagnostic criteria from DSM-III R, which required symptoms of both inattentiveness and hyperactivity/impulsivity, to DSM-IV, which only required either a predominantly inattentive, predominantly hyperactive/impulsive, or combined presentation. Several new ADHD medications also debuted during this period, providing physicians with more treatment options, such as the amphetamine Adderall and the non-stimulant atomoxetine. According to the IMS Health National Disease and Therapeutic Index, the number of ADHD diagnoses in adults also increased from 6.3 million in 2000 to 10.4 million in 2003, before plateauing between 9.5 and 10.6 million between 2004 and 2010 (Garfield et al. 110-116). Approximately 95% of these diagnoses resulted in pharmacological treatment.
The increase in ADHD diagnoses among children and adults raises concerns about the true prevalence of the disorder. Higher diagnostic rates may reflect more up-to-date diagnostic criteria that serve to reduce the number of false-negatives. On the other hand, some researchers have suggested that the rapid increase in prevalence rates indicates overdiagnosis (Batstra and Frances 486-488). A trend that parallels the increase in ADHD prevalence and that supports the hypothesis of overdiagnosis is the rise in direct-to-consumer advertising by pharmaceutical companies. After the US Food and Drug Administration loosened its regulations concerning direct-to-consumer advertising in 1997, the pharmaceutical industry increased its overall spending on marketing campaigns from $791 million to $4.8 billion in 2006 (Bell and Wilkes 110-128). Advertisements for ADHD medications that hit the market during the same period encouraged adults and parents of children to ask their physician if ADHD was the cause of common behaviors like inattentiveness, activeness or forgetfulness. The correlation between industry advertising and prevalence rates makes direct-to-consumer advertising a probable cause of overdiagnosis.
Since no empirical diagnostic standards exist for ADHD, however, it is impossible to determine whether the disorder is underdiagnosed or overdiagnosed. Furthermore, with the recent publication of DSM-5, new diagnostic criteria will change the medical community’s understanding of an accurate diagnosis.
DSM-5: Foreshadowing an Increase in Diagnosis
The publication of DSM-5 in 2013 represents a long anticipated update to the DSM-IV TR published in 2000. The fact that all references but one in the DSM-5 were published after the year 2000 testifies to the wealth of research published between the releases of the two versions.
Both the DSM-IV TR and the DSM-5 classify ADHD diagnoses into one of three categories: 1) predominantly inattentive, 2) predominantly hyperactive/impulsive, or 3) combined. Patients that receive an ADHD diagnosis must meet five criteria outlined in both versions of DSM. The first criterion concerns the number of symptoms that must manifest in a patient. In DSM-IV TR, the patient, whether adult or child, must manifest at least six of the listed symptoms for a period of six months or more in such manner that the symptoms prove to be “maladaptive.” In DSM-5, the same criteria apply, with the notable exception that patients over the age of seventeen need only display five, rather than six, of the symptoms to be diagnosed with the inattentive subtype. Because it decreases the number of symptoms required for diagnosis, this change will increase the rate of ADHD diagnoses for adults with the predominantly inattentive presentation.
The second diagnostic criterion in the DSM-IV TR requires that “some hyperactive-impulsive or inattentive symptoms that caused impairment were present before age 7 years.” A significant revision to this is the change in age of onset from “before age 7 years” to “prior to age 12 years.” According to the DSM-5 Work Group, this change comes in light of a number of reported cases of ADHD that began after age seven (Batstra and Frances 486-488). It also accommodates cases in which adults are unable to accurately recall their ADHD symptoms prior to age seven. Furthermore, it also addresses the difficulty of retrieving supporting school records from before age seven. A study by Polanczyk et al. (2010) determined that such a change in the age of onset from seven to twelve years resulted in an increased prevalence of 0.1% within a sample population. Though it may appear insignificant, such an increase would amount to 300,000 new cases within the United States (Batstra and Frances 486-488).
The three other diagnostic criteria in DSM require that symptoms exist in “two or more settings (e.g., at home, school, or work; with friends or relatives; in other activities),” that they cause “significant impairment in social, academic, or occupational settings,” and that symptoms do not occur exclusively in the presence of other mental disorders (American Psychiatric Association and Task Force on DSM-IV). These criteria have not changed significantly between the two versions of DSM.
Although DSM-5 enumerates the criteria that define ADHD and prompt diagnosis, it does not establish a protocol for physicians to determine whether the criteria are met. The absence of a diagnostic protocol in DSM-5 has meant that no widely accepted, standard diagnostic protocol for ADHD exists. Although other organizations and research groups have published guidelines for adoption, their recommendations have not become normative. (Asherson and UK Adult ADHD Network 41-53).
The lack of standard diagnostic guidelines for ADHD permits physicians to use whichever diagnostic approach they wish. To assess academic impairment, for instance, physicians should, according to the American Academy of Pediatrics (AAP), consult the student’s teacher (Wolraich et al. 1007-1022). But there are various ways to do so, each with a potential for overdiagnosis or underdiagnosis. A physician who asks the teacher to send a report detailing the student’s misconduct may believe that academic impairment is present. By contrast, a physician who asks the teacher to send a copy of the student’s grades may not determine academic impairment in an average student. The first case poses a risk for overdiagnosis because the physician only retrieves information about the student’s delinquent behaviors. In the second case, the physician may underdiagnose the disorder by not considering the disproportionate effort that a student with ADHD must exert in order to achieve average grades. This represents the variability in diagnostic outcomes based on different methods of assessing DSM criteria.
Nevertheless, many assessment tools exist to aid in the diagnosis of ADHD. Although no single tool can determine a diagnosis independently, it may inform the physician’s diagnostic appraisal. The use of structured interviews, for instance, standardizes the questions asked about each symptom outlined in the first criteria of DSM-5. One such tool currently under development is the Diagnostic Interview for ADHD in Adults (DIVA). DIVA not only prompts physicians to ask if the patient has experienced each of the nine symptoms of inattentiveness or impulsivity/hyperactivity, but also provides examples for each symptom. This allows physicians to probe further into each criterion and clarify how each symptom might manifest. The uniform approach to what questions the physician asks and which examples he uses to explain them reduces the variability of the diagnostic interview and the potential for overdiagnosis and underdiagnosis.
The explanatory examples also include behaviors from childhood, which allow the physician to simultaneously begin assessing the second diagnostic criteria—onset of symptoms before age twelve (Kooij and Francken). Following the symptomatic behavior assessment portion, DIVA includes 79 questions concerning the social, academic, occupational, economic, and psychological impairment caused by these symptoms. By doing so, DIVA thoroughly assesses the fourth DSM criterion as well. DIVA takes approximately one hour to complete and is currently undergoing validation studies in the United Kingdom.
In addition to structured interviews, quantitative scales may also help physicians diagnose ADHD in a consistent manner. One such scale intended for children is the Vanderbilt Attention Deficit/Hyperactivity Disorder Parent Rating Scale (VADPRS) and Teacher Rating Scale (VADTRS). The parent scale consists of 47 symptomatic behaviors, adapted from DSM-IV TR criteria, which the parent rates on a four-point scale based on how often the behavior occurs, with 0 being “never” and 3 being “very often.” This is followed by 7 questions assessing the child’s academic and social performance on a five-point scale, with 1 being “excellent” and 5 being “problematic” (National Institute for Children’s Health Quality). The teacher scale assesses the same behaviors and areas of performance as the parent scale, but adapts the examples to be more representative of a classroom setting. By providing teachers with a comprehensive, standardized scaling tool, physicians reduce overdiagnosis due to highlighting the child’s delinquent behaviors and avoid underdiagnosis due to reliance on the child’s grades.
In contrast to DIVA, which evaluates the first and second DSM criteria, VADPRS and VADTRS assess the DSM criteria regarding symptomatic behaviors and presence of symptoms in multiple settings. The DSM criterion of onset before age twelve does not apply to children, so assessment scales for children do not address this criterion.
Areas of Uncertainty
Many assessment modalities exist to aid in the diagnosis of ADHD, but few researchers have investigated the methods most frequently used by physicians. In examining the research literature on ADHD diagnosis, this review did not find any studies measuring the prevalence of different diagnostic instruments in clinical practice. Although some studies have recruited physicians to employ different assessment tools, these have mainly been used to validate the tools themselves, rather than survey physicians’ actual utilization of them. It is therefore impossible to determine whether current practices likely result in overdiagnosis or underdiagnosis. Consequently, recommendations for diagnosing ADHD cannot attempt to correct current practices. Rather, recommendations must stem from evidence-based studies of the assessment tools themselves and the risks of overdiagnosis, underdiagnosis and misdiagnosis present in each.
Current diagnostic guidelines from the DSM-5 and the AAP outline the criteria that doctors should assess without standardizing how they should assess it. The development of assessment tools may supplement physicians’ diagnostic appraisal, but cannot diagnose ADHD independently because each assessment tool addresses a limited number of DSM criteria. Some researchers have proposed diagnostic toolkits that combine various assessment tools to encompass the full range of diagnostic criteria (Asherson and UK Adult ADHD Network 41-53). Such toolkits may also suit different patient demographics. The inclusion of VADPRS and VADTRS, for instance, would be beneficial for diagnosing ADHD in childhood, but not in adults. Similarly, structured interviews such as DIVA would be beneficial for adult patients, but impractical for teachers of child patients. In order to have the greatest impact, diagnostic toolkits must be adopted as normative by standard guidelines such as the DSM. This would establish a standard diagnostic protocol that introduces uniformity to the diagnostic process, and would facilitate comparative studies of diagnostic efficacy between institutions that adopt the protocol.
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