Impact of the DSM-V Attention Deficit Hyperactivity Disorder Criteria for Diagnosing Children With High IQ

Abstract

This study compared the number of attention deficit hyperactivity disorder (ADHD) cases defined by Diagnostic and Statistical Manual (DSM)-IV versus DSM-V criterion in children who have learning or behavioral problems with high IQ. The medical records of children ≤15 years of age who presented with learning or behavioral problems and underwent a Wechsler Intelligence Scale for Children (WISC)-III IQ test at the Pediatric Outpatient Clinic unit between 2010 and 2015 were reviewed. Information on DSM-IV and DSM-V criteria for ADHD were derived from computer-based medical records. Twenty-eight children who had learning or behavioral problems were identified to have a full-scale IQ ≥120. Sixteen of these high-IQ children met the DSM-IV criteria diagnosis for ADHD. Applying the extension of the age-of-onset criterion from 7 to 12 years in DSM-V led to an increase of three cases, all of which were the inattentive type ADHD. Including the pervasive developmental disorder criterion led to an increase of one case. The total number of ADHD cases also increased from 16 to 20 in this group. The data supported the hypothesis that applying the extension of the age-of-onset ADHD criterion and enabling the diagnosis of children with pervasive developmental disorders will increase the number of ADHD diagnoses among children with high IQ.

Keywords

Attention deficit hyperactivity disorder high IQ Diagnostic and Statistical Manual-V learning problems behavioral problems pervasive developmental disorder

Introduction

Attention deficit hyperactivity disorder (ADHD) is one of the most common childhood developmental and behavioral disorders. The worldwide-pooled prevalence of ADHD is 5.29% (Polanczyk, de Lima, Horta, Biederman, & Rohde, 2007)—and this prevalence has significantly increased over the last decade (Visser et al., 2014). Doctors, health-care professionals, and qualified clinicians use the guidelines in the American Psychiatric Association's Diagnostic and Statistical Manual (DSM) to help diagnose ADHD. The latest version of the DSM (DSM-V) was published in 2013. The DSM-V includes revisions to the diagnostic criteria for ADHD with respect to the previous version, the DSM-IV. Although these revisions did not fundamentally change the definition of ADHD, i.e., the exact DSM-IV wording for all 18 symptoms was retained, there were two significant changes. First, the diagnostic age of onset was changed. Specifically, the statement “symptoms that caused impairment were presented before age 7” was changed to “several inattentive or hyperactive-impulsive symptoms were presented prior to age 12.” Second, pervasive developmental disorders (PDD, or autism spectrum disorder in the DSM-V) were no longer listed as exclusion criteria: a comorbid diagnosis with autism spectrum disorder is now possible. Thus, the new criterion for ADHD diagnosis does not exclude adolescents, adults, or children with PDD.

These changes in the DSM-V criterion have led to an increase in the number of people diagnosed with ADHD. For instance, one study found that the change in the DSM-V diagnostic criterion increased the prevalence of ADHD from 7.38% to 10.84% among children aged 12–15 years (Vande Voort, He, Jameson, & Merikangas, 2014).

The characteristic behaviors of high-IQ children are often similar to the symptoms of children with ADHD (Antshel, 2008; Budding & Chidekel, 2012; Katusic et al., 2012; Minahim & Rohde, 2015). Additionally, ADHD can be masked by such characteristics in high-IQ children, as these children generally perform well in school and/or do not cause any problems for their teachers (Mullet & Rinn, 2015). Therefore, they may visit a doctor in later development or not at all (Pfeiffer, 2009). Data indicate that an ADHD diagnosis based on the DSM-IV criteria can be accurate for many high-IQ children (Antshel et al., 2007). Prior to the DSM-V, it was widely accepted that the DSM-IV diagnostic criteria could be applied to high-IQ children (Cordeiro et al., 2011). However, the way in which the changes in DSM diagnostic criteria have affected the diagnosis of ADHD in high-IQ children is not well understood.

As a consequence, we investigated the effect of changing the criteria for diagnosing ADHD in high-IQ children. We hypothesized that the two revisions—an increase in the age of ADHD onset and the inclusion of children with PDD in the ADHD criteria—will increase the number of high-IQ children who are diagnosed with ADHD.

Method

The study was conducted using data collected between January 2010 and May 2015 at the Pediatric Outpatient Clinic of the Department of Pediatrics, Prince of Songkla University. Permission from the institution review board of the university was obtained to conduct the study. A diagnosis of ADHD was made only after an initial meeting with a pediatric resident and developmental and behavioral pediatrician, who interviewed children who presented with learning or behavioral problems using the semi-structured DSM-IV checklist on the computer-based medical records. The diagnosis relied on the documentation of symptoms that were associated with clinical judgments of functional impairment relative to the typical child from multiple situations according to the DSM-IV criterion. All school age children who had learning or behavioral problems presented in our clinic were examined by trained psychologists, who performed IQ assessment with the Wechsler Intelligence Scale for Children-III Thai version (WISC-III). The resulting data were stored in a computer database, and a researcher reviewed the computer-based medical records of all children who had an IQ ≥120.

The researcher reviewed the results of the evaluations according to the DSM-IV, including the diagnostic summaries for children who were interviewed by both the pediatric resident and the developmental and behavioral pediatrician. Information regarding the age of onset of the disease and comorbidities, including PDD, was included in the computer record. Two researchers recorded the number of points that corresponded to the DSM-IV criteria, the age of onset of the disease, and any comorbidity. Discrepancies in the data were resolved in a research team meeting and by consensus.

To determine whether the patient symptoms matched the DSM-V criteria, we checked the age of onset and whether the patient had any of the associated diseases that could not be diagnosed together with ADHD according to the DSM-IV, especially PDD.

Results

A total of 825 children with learning or behavioral problems had been examined and completed the WISC-IIII at the Pediatric Outpatient Clinic of the Department of Pediatrics, Prince of Songkla University. Of these, a total of 28 children had full scale IQ (FSIQ) ≥ 120. The information related to the diagnosis of the cases was shown in Table 1. Most of the high-IQ children were male (82%). The average age of onset and diagnosis was 6.3 and 8.6 years, respectively. The mean WISC-III FSIQ score of the high-IQ children was 127 ± 5.3 (Table 1). A total of 16 of these high-IQ children (61%), 12 of whom were male, were diagnosed with ADHD according to the DSM-IV criteria. Once the DSM-V criteria checklist was used, 20 children had symptoms of ADHD. Of the four additional children, three were between 7 and 12 years, i.e., 8, 8, and 9 years. All three were males who had the “inattentive” subtype of ADHD and were diagnosed with ADHD without any comorbid illness. The other child was a male who had experienced symptom onset when he was under seven and met the other DSM-V criteria, but had initially failed to match the DSM-IV criteria because of a previous diagnosis of PDD.

Table 1.

Clinical and demographic characteristics of the 28 high-IQ patients.

Patient #	Age onset (years)	Age at diagnosis (years)	Sex	WISC-III FSIQ	VIQ	PIQ	Disorders	Inattention symptoms count	Hyperactivity symptoms count
1	6	8	Male	126	113	135	LD	nd	nd
2	3	6	Male	126	131	116	PDD	nd	nd
3	6	6	Female	132	128	132	ADHD-I	8	4
4	6	6	Male	138	127	144	ADHD-H	4	6
5	6	11	Male	126	118	131	ADHD-I, LD	6	3
6	5	7	Male	135	134	126	ADHD-C	8	7
7	8	12	Male	135	134	135	ADHD-I (based on DSM-V)	7	3
8	5	7	Male	122	108	130	ADHD-C, LD	7	6
9	6	9	Male	126	113	135	PDD	4	2
10	9	9	Male	128	117	136	N	4	0
11	4	10	Male	133	132	129	ADHD-I	7	2
12	6	8	Male	137	127	141	ADHD-I, LD	6	4
13	6	9	Male	130	128	127	ADHD-I	8	3
14	5	9	Male	135	127	139	ADHD-C, LD	7	8
15	6	10	Male	122	115	126	ADHD-C, LD	9	8
16	8	8	Male	120	110	127	ADHD-I (based on DSM-V)	8	4
17	11	11	Male	122	114	126	N	nd	nd
18	7	7	Male	127	124	126	N	4	0
19	4	8	Male	122	121	122	ADHD-I, LD	7	3
20	6	7	Male	123	122	123	ADHD-I	8	4
21	6	11	Male	127	128	120	ADHD-C (based on DSM-V), PDD	6	6
22	8	8	Female	127	126	125	N	nd	nd
23	6	8	Male	123	118	125	ADHD-I, LD	7	2
24	6	10	Female	127	125	126	ADHD-C	8	7
25	4	10	Female	121	112	123	ADHD-I	7	0
26	3	8	Female	121	124	122	ADHD-C, LD	7	6
27	7	7	Male	123	124	119	N	nd	nd
28	9	10	Male	128	129	121	ADHD-I (based on DSM-V)	6	0

Note. WISC-III: Wechsler Intelligence Scale for Children-Third Edition; FSIQ; full scale IQ; VIQ: verbal IQ; PIQ: performance IQ; nd: was not determined; ADHD-C: attention-deficit/hyperactive disorder combined type; ADHD-H: attention-deficit/hyperactive disorder hyperactive-impulsive type; ADHD-I: attention-deficit/hyperactive disorder inattentive type; LD: Learning disorder; PDD: Pervasive developmental disorder; N: did not meet DSM-IV or DSM-V diagnostic criteria for psychopathology.

Discussion

In this study, we compared the DSM-IV and DSM-V criteria for diagnosing ADHD in high-IQ children. The data indicated that applying the new criteria could increase the number of individuals diagnosed with ADHD by up to 14%. This increase was mostly due to the increase in the age of onset to include children aged between 7 and 12, although we found one child that would have been excluded based on the DSM-IV criteria due to being previously diagnosed with PDD. When compared to the Vande Voort et al. (2014), data found 31% increased, in adolescent population of 12–15 years of age, these data suggested that ADHD prevalence rates increased less robustly in the high-IQ population of 6–12 years of age at presentation. It was not surprising because expansions of age-of-onset criteria were more affected in the older population.

All three new cases included according to the change in the age of onset in the DSM-V criteria had the “ADHD inattentive” subtype. This finding was in agreement with a previous study, which found that the expanded age of onset in the DSM-V led to an increase in the number of diagnoses of the ADHD inattentive subtype (Vande Voort et al., 2014). However, the proportion of inattentive subtype cases in this study was higher than that in the previous study (Vande Voort et al., 2014). It is possible that the combined type cases with serious symptoms generally have lower FSIQ, thereby excluding them from the initial sample (Baum, Olenchak, & Owen, 2004; Hartnett, Nelson, & Rinn, 2004; Kaufmann, Kalbfleisch, & Castellanos, 2000).

It was expected to find an increased number of individuals who were newly eligible for an ADHD diagnosis due to comorbid PDD. However, we only found three cases of ASD with FSIQ ≥ 120, making our sample quite small. Previous study showed that children with high IQ and PDD characteristics were at risk of not being assessed and consequently delayed intervention (Assouline, Foley, & Doobay, 2009). It could cause an increase in awareness of early assessment and start the intervention to children with high IQ and PDD.

All four patients included under the new criteria were male. This differed from a previous study, which found a higher proportion of females when using the DSM-V criteria compared with the DSM-IV criteria (Vande Voort et al., 2014). However, we had a small number of female cases, and so it is not possible to make any strong claims about sex differences. The study by Vande Voort et al. (2014) that found more females with ADHD was a population-based study (unlike this study, which was a hospital-based study), so the proportion of males was much higher from the beginning.

In the present sample, the most common condition associated with ADHD was learning disorders. This was surprising because there were no other common comorbidities found, i.e., oppositional defiant disorder, conduct disorder, anxiety disorder, or depression disorder. This is probably because this study was conducted in a Pediatric Outpatient Clinic. In tertiary care hospitals in Thailand, children with severe behavioral problems usually receive treatment at a psychiatric clinic for children without going to the Pediatric Outpatient Clinic. As a result, few children with comorbid psychiatric disorders were likely to seek treatment at our facility.

There are several important limitations to this study. First, the study was retrospective, so some demographic information was missing for some of the cases. However, cases that were missing the key information were not included. Second, the study sample included only 28 high-IQ cases from a total of 825 children with developmental and behavioral problems. The subgroup of high-IQ children comprised only 3.4% of the total sample, which was less than would be expected. Previous studies have revealed that about 5% of children with developmental and behavioral problems have a high IQ (Cordeiro et al., 2011). Third, we did not compare our sample to children with a normal intellectual level to determine whether the size of this group would increase according to the new diagnostic criteria. This should be examined in future studies. Fourth, this study was conducted in children with behavioral, developmental, and learning problems who were referred to a Pediatric Outpatient Clinic at a tertiary hospital. Thus, caution should be used in expanding the results to the general population.

Despite the limitations mentioned above, this study demonstrated the effect of the new ADHD diagnostic criteria in the DSM-V on high-IQ children. As with previous studies in teenagers in which the age criteria and scope of ADHD diagnosis were expanded, the changes in the DSM-V caused an increase in the number of patients diagnosed with ADHD. Using the DSM-IV diagnosis criteria, it is possible that 14% of high-IQ children with ADHD will not receive an appropriate diagnosis. On the other hand, over inclusion should be concern to use DSM-V ADHD criterion in this group. However, further research is necessary to fully explore this possibility.

Footnotes

Acknowledgments

The authors are grateful to the participants and their families.

Article Notes

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