Comorbidity in Adult ADHD: An Expert Interview With Lenard Adler, MD

Editor's Note:

Adults with ADHD often are affected by co-occurring psychiatric conditions. The type of comorbidity varies and includes anxiety disorders, unipolar and bipolar mood disorders, conduct and antisocial personality disorders, and substance use disorders. These disorders can complicate both diagnosis and management of ADHD, as well as those of the co-occurring disorder. To gain more perspective on adult ADHD and comorbid psychiatric disorders, Medscape Editor Priscilla Scherer spoke with Lenard Adler, MD, Associate Professor of Psychiatry and Neurology and Director of the Adult ADHD Program at New York University School of Medicine in New York City.

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Medscape: Studies looking at the prevalence of psychiatric comorbidity of ADHD have produced varying results. For example, the National Comorbidity Survey Replication Study^[1] found that among individuals diagnosed with depression, bipolar disorder, or anxiety disorders, the rates of ADHD were 32%, 21%, and 9.5%, respectively. But your own analysis of medical and prescription claims found that no more than 2.5% of patients who were filing claims for depression, bipolar, and anxiety-related illnesses also had a documented diagnosis of ADHD.^[2] Thus, the rates of ADHD and comorbid mood and anxiety problems were very high in a community survey, but in prescription claims and medical claims the rates were very low, which suggests that adult ADHD is not well recognized and is undertreated in the community. What do you think is the biggest barrier to accurate diagnosis of ADHD in adults?

Lenard Adler, MD: Well, we always try to start with an appropriate diagnosis. I think the data that you mentioned highlight the fact that comorbidities with ADHD are very common, and they are more often the rule rather than the exception. The data from the National Comorbidity Survey really highlight very high rates of depressive disorders, bipolar disorder, and anxiety disorders. In addition we tend to see substance use disorders and learning disabilities that tend to co-travel with ADHD. The claims data that you mentioned show -- and, again, these are just claims data, the diagnoses are not verified -- that for patients who are receiving treatment for depression, bipolar disorder, and anxiety-related disorders, there were very, very low rates of documented diagnosis of ADHD. So this highlights the fact that there are a number of individuals who are being treated for these other disorders who probably have ADHD, and the ADHD is being missed. And, in fact, this has been shown in a variety of other studies, including the National Comorbidity Survey, which did find that a substantial number of individuals who turned out to have ADHD actually had seen a healthcare practitioner in the last year, and the ADHD had been missed.

Why is this so? It's an area of burgeoning research. Several years ago, we surveyed 400 primary care physicians who treated mental health disorders, anxiety disorders, and depressive disorders, and asked them about their understanding and training regarding ADHD.^[3] We found they were twice as comfortable treating depression and anxiety disorders as they were treating ADHD. And, in fact, they had received much less training in the management of adult ADHD than for the other mental health disorders. So there is a knowledge gap here, in part.

Second, a historical issue needs to be brought forward. ADHD was not conceptualized as an adult disorder and was thought of as being only a childhood disorder until the mid-1970s; it didn't enter our diagnostic lexicon as an adult disorder until 1987. We now know that about 2 out of 3 children with ADHD become adults with ADHD. So there's work to be done in bringing the medical community up to speed in our understanding of ADHD in adults.

Medscape: Do you think diagnosis is more difficult when the patient has a comorbid mood disorder?

Dr. Adler: Well, I think it's important to make accurate diagnoses for adults whether there's mood disorder accompanying the ADHD or not. The longitudinal history is critical in making the diagnosis and will help differentiate between what may be a comorbid disorder and what may be ADHD. Mood disorders tend to be episodic, whereas ADHD symptoms tend to be present throughout the life span.

Medscape: Some adult psychiatrists have mentioned that they became interested in adult ADHD as a result of seeing patients who came in with depression, and who actually also had ADHD. In your experience, is depression a hallmark of ADHD in adults?

Dr. Adler: I don't think depression is necessarily a hallmark of ADHD. We have to be clear in distinguishing what is a co-traveling comorbid condition, meaning co-occurring, and what is a symptom. Not all individuals who are dysphoric and have some elements of depressed mood meet the criteria for major depression or chronic depression (dysthymia). You need to be very careful in distinguishing what is a comorbid disorder and what isn't. I don't think that major depression is a symptom of ADHD. I do think that chronic dysphoria can result from having untreated ADHD. So it's important to classify what type of depression we're talking about. It does influence which kind of treatment you're going to initiate first, because the general rule of thumb is that you treat the most impairing condition first, be it the co-occurring condition, the comorbid condition, or the ADHD.

So in distinguishing between major depression and ADHD, if patients have major depression they're going to have episodic periods where they will be clear of vegetative symptoms of sleep disturbance, appetite disturbance, dysphoria, and sexual dysfunction. And if there is some dysphoria from the ADHD being untreated, that would be a more chronic condition, so that overlap would come much more, let's say, with dysthymia. But again, I don't think that depression itself is a hallmark feature of ADHD.

Medscape: Going back to The National Comorbidity Survey, it found that nearly 20% of patients with ADHD also have bipolar and roughly 21% with bipolar also have ADHD. Some questions we hear from child psychiatrists concern children who were originally diagnosed with ADHD, who actually end up with a diagnosis of bipolar because of symptom overlap. Is this also the case with adults with ADHD? Or is bipolar disorder more easily differentiated from ADHD in adults?

Dr. Adler: I'm not sure that the childhood data for bipolar disorder and ADHD -- the comorbidity that's occurring there and the co-occurrences -- I'm not sure it's from symptom overlap. There are very, very high rates of ADHD in children who have been diagnosed with bipolar disorder. So it's not just symptom overlap; these are true co-occurring conditions. For adults, rates of bipolar disorder tend to be high also. It's important to make this recognition of bipolar disorder and ADHD, because data from the STEP 1000 [Systematic Treatment Enhancement Program] study^[4] show that individuals who have bipolar disorder and ADHD have a different course of their bipolar disorder. They tend to have more episodes, earlier onset, and more substance use. So making these accurate diagnoses is critical in terms of trying to formulate an intervention -- an early intervention, and an effective one.

Medscape: What is the best approach, then, for patients with comorbid ADHD and bipolar disorder? I think there has been some concern that stimulant treatment could exacerbate bipolar symptoms, and I'm wondering whether there is any evidence for that.

Dr. Adler: This is an area of burgeoning research, that we're examining going forward . The evidence here is small. Some of the data do support judicious use of stimulants in patients with bipolar disease.^[5,6] If the patient has significant bipolar illness, you're going to want to stabilize the mood first, and then attempt to treat the ADHD. So, again, we're looking at the general paradigm that you treat the most impairing disorder first, stabilize that, and then take a look and see what's left.

Medscape: Given the association of oppositional defiant disorder and conduct disorder with ADHD in childhood, how often does personality disorder complicate the diagnosis and treatment in adults?

Dr. Adler: Personality disorders are comorbid with ADHD in adults. Antisocial personality disorders have been noted to occur. Generally, it is felt that those are individuals who have had conduct disorders and have gone on to develop antisocial personality disorders. This does not mean that a large percentage of the population with ADHD actually has antisocial personality disorder. It is an associated disorder, though. It's important to again take a look at longitudinal diagnoses, go back and take a childhood history. For many patients with antisocial personality disorder, there will be a childhood history of conduct disorder, and, again, when treatment planning, the concept is to treat the most impairing disorder first.

Medscape: Finally, one of the most controversial comorbidities with ADHD is substance use disorder. How do you approach patients with comorbid ADHD and substance use disorder?

Dr. Adler: Substance use disorders are highly comorbid with ADHD. A percentage of that may relate to patients self-medicating with substances to treat their ADHD. A study out of Massachusetts General Hospital took a look at 2 groups of adolescents with ADHD who were followed longitudinally -- 1 treated for their ADHD and 1 not -- and found that the substance use rates in the untreated ADHD group were about twice as high as [the rates in] the group that was treated with psychostimulants.^[7] That's an important piece of data. So, again, we're talking about early recognition of ADHD and initiation of treatment to affect the longitudinal course.

However, we do know that for young adults in the college-age population, there is misuse and diversion sometimes of short-acting stimulant medications. We tend to use the longer-acting stimulants in our adult patients because we want to treat them throughout the day. A survey by Wilens^[8] from Mass General did find that the diversion, if it occurred, was more common with short-acting stimulants as compared to the longer-acting ones. So that is an important clinical point, to try to initiate treatment with a longer-acting stimulant if you choose to use that. However, if the patient has active substance use at this point in time, it's important to identify that and also bring that under the umbrella of treatment. The data support that it is difficult to treat the ADHD unless the substance abuse is engaged. Also, if the substance abuse is active, it is probably prudent to initiate treatment first with a nonstimulant, primarily atomoxetine, which has not been shown to have abuse liability.

Supported by an independent educational grant from Shire.