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October 17th 2003

Subtypes in ADHD: A Newsmaker Interview With Mary Solanto, PhD

Robert Kennedy and Robert Glassman

Oct. 17, 2003 Editor's Note: Attention deficit-hyperactivity disorder (ADHD) has become an important area in child and adolescent psychiatry. Much of the new research has delved into the various diagnostic subtypes, response to treatment, and cognitive styles of both children and adults diagnosed with ADHD.

To discuss this new research, Medscape spoke with Mary Solanto, PhD, an associate professor of psychiatry in the Division of Child and Adolescent Psychiatry at Mt. Sinai School of Medicine and director of ADHD Clinic at Mt. Sinai Medical Center in New York City.

Medscape caught up with Dr. Solanto at the annual meeting of the American Academy of Child & Adolescent Psychiatry in Miami Beach, Florida.

Medscape: You presented a poster here in Miami on ADHD subtypes. Can you tell us about it?Dr. Solanto: We are doing a lot of research trying to understand what may be critical differences between the two most recognized types of ADHD. There are kids who are predominantly inattentive, who've only been recognized recently in the DSM-IV, and then there is the more commonly recognized child with ADHD that is also hyperactive and impulsive. There seem to be many differences in the behavioral functioning of these children and possibly in the kinds of deficits they're likely to experience. We're evaluating these children on a whole array of neuropsychological measures. What we reported on were some differences on the WISC [Weschler Intelligence Scale for Children] and we looked at whether there were differences on measures of processing speed, which is how quickly a child can respond to a task and complete it, as well as measures of distractibility.

Parents and teachers often report that kids with this inattentive type are very sluggish, they're very slow to accomplish many things, homework among them. And other kids often observe that they are very slow to respond interpersonally. You ask them a question and you don't even know if they heard you, and they are looking around and daydreaming. [Their peers] may not have patience for that kind of behavior. These kids can suffer socially as well.

What we showed on the WISC was that there was a much higher proportion of kids with this inattentive type who did very poorly on the processing speed index. They were more likely to have a big discrepancy between their verbal functioning and their processing speed. They were also more likely to have a big discrepancy between their verbal functioning and their freedom from distractibility index on that test. That seems to verify the kinds of behaviors that we observed interpersonally with these kids, and it also provided a way for them to be assessed in a more formal manner to differentiate which type of ADHD they may have.

Medscape: Has anyone else done similar studies? Dr. Solanto: There have been some reports in the literature of longer reaction times of these kids in laboratory tasks. There was also one other study that suggested a difference in processing speed. This is the first time where it has been demonstrated on commonly used tests that are used in psychological evaluations. What we want to do now is see if we can understand more about why processing is slower for these kids. Is it occurring on the input side, in terms of their ability to orient to a stimulus and process that stimulus, or is it occurring on the output side where they are processing the task and then deciding or executing a particular response? Other tests in the battery will hopefully shed more light on what is causing the longer reaction time. Another possibility is that they take longer to retrieve information and to call up the appropriate information for the task at hand. We'll also be looking at that as a potential mediator.

Future studies will look at whether these children respond differently to stimulant medication than children with a combined type or perhaps they may require a different dosage. We are also collecting fMRI studies to look at whether different portions of the brain are activated in children with the two subtypes, particularly when they are doing a task that requires inhibitory control. We have data that will hopefully help to elaborate differences between the subtypes and ultimately construct treatments that are more targeted for their particular deficits.

Medscape: Is this a particular age group or is it the spectrum of children and adolescents? Dr. Solanto: That's an interesting issue. Studies show that the age of onset or at least the age at which children with the inattentive subtype are recognized is much later. They often do not come to clinical attention till ages 9 to 11, and it may be hard to document that there were symptoms before that. It has been proposed that the criterion for onset should be higher for the inattentive. Why this should be the case isn't entirely clear. It could be that demands on attention don't increase so that these children don't look impaired in the classroom until they get to be 9 years old because they are not behaviorally disruptive, they don't have other problems. Their problems are primarily on structured tasks that require concentration and focus. It is possible that this is a subtype that does not have an onset until later. In the study, the children were matched for age, so that wouldn't account for differences. The age range for both subtypes was 7-12 years old.

Medscape: Could you tell us about your ADHD clinic and some of the things you do in the program? Dr. Solanto: We see the whole range of ADHD at the program at Mt. Sinai. Children, adolescents, and increasingly, more adults, who sometimes recognize in themselves the symptoms that their children have, because as you know ADHD is highly heritable. Often they can see they have experienced difficulties similar to [those of] their child and sometimes, with a little encouragement, they will come forth for an evaluation for themselves.

In the clinic, we provide follow-up treatment in the way of medication [and] individual behavior therapy, which is done by coaching parents and teachers in how best to respond and how to manage these behaviors.

We also have a group that teaches adults time management and organizational skills that they may have not developed because of the impairments associated with ADHD, which is very hard to acquire later on without specific coaching. Not even medication will fully address that. It may help them learn these new strategies, but it is something they have to work at and have help with. The groups have done pretty well, they seem to have a positive impact. Next we will evaluate the whole process in a more rigorous fashion.

Medscape: Adult ADHA seems to have a new focus, in the literature and even in the press. People are making it seem like it is a new diagnosis, which it isn't. Can you address that? Dr. Solanto: The follow-up studies have shown as many as half of kids with ADHD will continue to have many symptoms in adulthood, if not the full-fledged disorder. We knew these people were out there, they had to be given the results of these longitudinal studies. They might not be recognized by mental health professionals because they often have many other symptoms and problems that by time they reach adulthood take precedence. Many are depressed or have problems with anxiety, and often those are the conditions and the problems that are recognized if they go for consultation, and unless one takes a very careful history beginning at childhood, one may overlook the fact that there were certain ADHD symptoms that are present very early on and have continued into adulthood. So it's good that there is now much more publicity about it, there are some books that are very helpful to adults in helping recognize problems they may have had. There are actually very few specialized centers, even in Manhattan, that do evaluations and treatment of adults with ADHD.

Medscape: I notice that the researchers in the field of ADHD are a small group and there seems to be a great deal of collaboration. Do you work with other researchers in other areas in New York as well as in the rest of the country? Dr. Solanto: It's really important to exchange ideas and share findings and instruments that are used for diagnosis, as well as strategies for intervention. We're working with adults to develop organizational skills. For example, Howard Abacoff, at New York University, has developed a superb program to teach children how to better organize themselves and has gotten really excellent results. There is an exchange of ideas and approaches that benefits everyone involved, and it is great to do that at a meeting like this, especially one that is provided in such a gorgeous environment.

Reviewed by Gary D. Vogin, MD

Robert Kennedy is site editor of Medscape Psychiatry; Robert Glassman is a freelance editor for Medscape.

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