Similarities and Differences Between ADHD Subtypes

by Dr. David Rabiner

In the current diagnostic scheme for ADHD, 3 different subtypes have been identified. ADHD, predominantly inattentive type is the diagnosis assigned to children who display multiple inattentive symptoms, but few hyperactive/impulsive symptoms. These are the children who used to be diagnosed as ADD without hyperactivity. Children who display multiple hyperactive/impulsive symptoms but few inattentive symptoms are classified as ADHD, predominantly hyperactive/impulsive type while those who show both sets of symptoms are diagnosed with ADHD, combined type.

A study published in the Journal of the American Academy of Child and Adolescent Psychiatry takes a careful look at the similarities and differences between children with these different subtypes of ADHD (February, 1998). This is a very interesting article and here are some of the highlights:

• The combined type group is the most common, occurring in 61% of identified cases compared to 30% for the inattentive type and 9% for the hyperactive impulsive type.

• For each subtype, there was a significant time lag from when symptoms were first evident to when the child was referred for treatment. This ranged from 1.9 years for the hyperactive/impulsive type to 4.4 years for the inattentive type. This is an extremely important and disturbing finding because it indicates that most children with ADHD do not receive any treatment until several years after their symptoms were first apparent. As a result, both children and parents are struggling unnecessarily for an extended period before any professional help is obtained.

• Children with the combined type had higher rates of behavior disorders (conduct disorder and oppositional defiant disorder) than the other two subtypes. They also had higher rates of bipolar disorder. Even children who had the inattentive symptoms only, still had higher rates of these disorders than children without ADHD.

• Children in the different groups did not differ in how often they were diagnosed with an anxiety disorder. Children with the combined type or inattentive type were more likely to be depressed than children with the hyperactive/impulsive subtype.

• On average, all three groups scored lower than non-ADHD children on measures of intellect, academic functioning, and social functioning. Children with different subtypes of ADHD did not differ from one another on any of these dimensions.

This study is valuable for several reasons. First, it provides validation for the current diagnostic system in which 3 different types of ADHD are listed. Because differences in children’s functioning was related to which type of ADHD they had, the different diagnostic groupings actually reflect important differences between children and not just labels that don’t relate to anything that really matters.

The study also highlights that children with the combined type diagnosis (those who show both inattentive and hyperactive/impulsive symptoms) are likely to be at greater risk for other psychiatric disorders (specifically conduct disorder, oppositional defiant disorder, and bipolar disorder). Parents whose child has the combined type diagnosis need to be especially vigilant about these other kinds of difficulties. Speaking specifically with your child’s physician and/or psychologist about ways to minimize the chances of these other conditions developing can be quite important.

I want to emphasize again that for children with ADHD, it is often the behavior disorders, emotional problems, academic struggles, and social difficulties that develop in response to the primary ADHD symptoms that have the most negative, long-term impact on the child’s development.

If your child is struggling in any of these areas, it is essential that these difficulties be specifically addressed in treatment. Although ADHD often contributes to the development of these problems, such problems are not the same thing as ADHD. I have seen many parents who believed that all of their child’s problems were part of their ADHD, and that since their child was already taking medication they assumed that nothing else could be done. This is definitely not the case. Making sure that such difficulties are specifically addressed in a child’s treatment plan is one of the most important things parents can do to promote their child’s healthy, long-term development.
 

About The Author

Dr. David Rabiner is a Senior Research Scientist conducting research on ADHD and children's social development at Duke University.

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