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What Other Disorders Tend to Occur with the Different Subtypes of ADHD?
An extremely important issue in promoting the healthy development of a child with ADHD is paying careful attention to the other behavior and/or emotional difficulties that often co-occur with ADHD. These can include such other conditions as Oppositional Defiant Disorder (ODD), Conduct Disorder (CD), Major Depressive Disorder (MDD), and various types of anxiety disorders. Thus, for many children with ADHD, the most effective treatment is likely to require that specific attention be focused on these "co-occurring" problems, in addition to the primary ADHD symptoms of inattention and hyperactivity/impulsivity.
In a recently published study (Willcutt, E., et al., (1999). Psychiatric comorbidity associated with DSM-IV ADHD in a nonreferred sample of twins. Journal of the American Academy of Child and Adolescent Psychiatry, 33, 1355-1362) some very interesting data is presented on the types of other psychiatric disorders that are more likely to be present depending on the subtype of ADHD that a child has been diagnosed with.
As you may be aware, the current diagnostic criteria for ADHD specify 3 distinct ADHD subtypes. ADHD, Predominantly Inattentive Type, is the diagnosis given to children who display prominent inattentive symptoms but relatively few symptoms of hyperactivity/impulsivity. These are the children who people sometimes refer to as "ADD", although it should be noted that the term ADD or Attention Deficit Disorder is no longer technically correct.
ADHD, Predominantly Hyperactive/Impulsive Type applies to children who show high levels of hyperactive/impulsive behavior but relatively few inattentive symptoms. Finally, there is a final category called ADHD, Combined Type that is used for children who display high levels of both inattentive behaviors and hyperactive/impulsive behaviors. (For a complete presentation of current diagnostic criteria for these subtypes go here.)
The Current Study
The participants in this study were part of an ongoing study of learning disabilities in a large sample of twins. Parents of all known twins from 27 school districts within a 150 mile-radius of the Boulder/Denver, Colorado, area were contacted about participating. For parents who consented, an initial screening based on teacher behavior ratings was used to identify potential cases of ADHD. These children then received a thorough diagnostic evaluation to determine whether the child actually had ADHD and which subtype was the appropriate diagnosis. In addition, these children were given tests to estimate their level of intellectual ability, and information was obtained from parents, teachers, and children themselves to determine whether CD, ODD, MDD, or Generalized Anxiety Disorder (GAD) were also appropriate diagnoses for the child. (GAD is a type of anxiety disorder that is characterized by persistently excessive levels of anxiety/worry about a variety of different areas including worries about school performance, getting along with others, performance in extracurricular activities such as sports or music, etc.).
The characteristics of the final sample are shown below. The important thing to note is that this is a sample of children obtained from the community rather than from a clinical setting. Thus, the data reported are more likely to be representative of children with ADHD in general community settings as opposed to children with ADHD who are seen in a specific mental health setting. There is some question, however, about whether data obtained from a sample of twins can be generalized to children with ADHD who are not twins. (HI stands for hyperactive/impulsive).
As can be seen above, the hyperactive/impulsive subtype (HI) is clearly the least frequently occurring subtype in this community sample. This results replicates findings from several other studies that have been published recently. Overall, females made up about 32% of the children who were found to have ADHD. Thus, the ratio of boys to girls with ADHD was about 2:1. About 66% of the girls with ADHD were diagnosed with the inattentive subtype while about 50% of the boys were diagnosed with the inattentive type of ADHD.
Although there were no significant differences in socioeconomic status (SES) between any of the ADHD groups and the control participants, some very interesting differences in IQ were found. Children with both the inattentive and combined type of ADHD had lower IQ scores - on average - than did children in the control group. The average IQ score for children with the hyperactive/impulsive subtype of ADHD, however, was actually slightly higher than children in the control group. (It is important to note that the lower average IQ scores for children with the inattentive and combined subtypes of ADHD does not mean that these children tend to be less "bright" than other children. The average scores for children in these groups was almost exactly 100, which is the score that falls at the exact mid-point for children taking this test. Thus, the children in the control group and the HI group actually had scores that were significantly above average, although why this would be the case is unclear.)
Next, the authors examined the percentage of children in each group who had any of the other diagnoses that were assessed. These results are shown below. The number on left of the "/" indicates the actual number of children in the group who had the diagnosis and the number on the right side of the "/" indicates the % of children in the group that this represents. For example, the entry of 9/10 in the upper left-hand corner indicates that 9 children in the control group, which represents approximately 10% of that group, were diagnosed with ODD.
Several aspects of these results are noteworthy. First, for the diagnoses of ODD and CD - the two types of disruptive behavior disorders - children with any subtype of ADHD were more likely to receive the diagnosis than control participants (i.e. those without ADHD). Children with the Combined Type of ADHD, however, were even more likely than children with the Inattentive Type or the Hyperactive/Impulsive Type to receive these diagnoses. (For a more thorough discussion of ODD and CD click here.)
For the 2 types of emotional disorders - MDD and GAD - the results were different. For GAD, it actually turned out that children with ADHD were not significantly more likely to receive this diagnosis than were control participants. Thus, even though the percentages look a bit higher for the Inattentive and Combined Types relative to the control group, these differences are no greater than what would be expected by chance.
Children with the Inattentive Type of ADHD and children with the Combined Type of ADHD were both more likely to be diagnosed with depression than were control children. Interestingly, they were also more likely to be diagnosed with depression than were children with the HI subtype of ADHD, none of whom were diagnosed with depression.
It is also very important to note that when examining children's own reports about the amount of sadness and distress they experienced, it was only children in the Inattentive group who reported high levels of distress.
Summary And Implications
Overall, the results of this study clearly indicate that children with ADHD are at increased risk for other behavioral and emotional disorders. Thus, it is quite important when evaluating a child for ADHD that careful attention is given to obtaining a comprehensive assessment of the child's overall emotional and behavioral functioning, rather than focusing exclusively on the question of whether or not the child has ADHD. This would hold true when evaluating adolescents and adults for ADHD as well.
It also appears that the inattentive and hyperactive/impulsive symptoms of ADHD are associated with increased risk for different types of problems. Symptoms of hyperactivity/ impulsivity and the HI subtype are primarily associated with symptoms of other disruptive behavior disorders. In contrast, symptoms of inattention and the Inattentive type of ADHD are associated with an increased risk of depression and perhaps with lower levels of cognitive functioning. (It should be noted that other researchers have reported that it is problems with attention, and not problems with hyperactivity/impulsivity, that are most strongly associated with academic difficulties in children with ADHD).
This latter finding seems especially important given the fact that many children with the inattentive subtype of ADHD often do not display major behavior problems. As a result, these children are more likely to "fall through the cracks" and receive no treatment at all, or, to be treated by primary care physicians alone rather than by mental health specialists.
The concern here is that prior research on the care provided by primary care physicians to children with ADHD suggests that they often do not conduct the type of thorough evaluation that is required to identify a non-obvious problem like depression. Thus, many children with the Inattentive subtype of ADHD who are also depressed may fail to get the type of help that they require. I think the important take-home message here is to pay very careful attention to the emotional functioning of children and teens with the Inattentive subtype of ADHD, about 1 in 4 of whom may be depressed based on the data from this study. When a child is depressed, consultation with a child mental health professional is important to pursue.
For children with the Combined type of ADHD this is also quite important. Because these children often have important co-occurring behavior problems like ODD or CD, their depression may tend to be overlooked for a different reason - i.e. everyone is so focused on the ADHD symptoms and behavior problems that the child or teen's depression gets overlooked. This can also result in the child's receiving incomplete and less than optimal treatment. Thus, in both cases, the best remedy for these potential problems is to be certain that a thorough and comprehensive evaluation is conducted in the first place. For a set of suggested guidelines of what such an evaluation would entail, click here. You can also find a discussion of depression in children here.
Note: This article originally appeared in Attention Research Update, an online newsletter written by Dr. David Rabiner, a Duke University psychologist and former member of CHADD's Professional Advisory Board. You can learn more about Attention Research Update and sign up for a free subscription at www.helpforadd.com.