Russell A. Barkley, PhD (RB) is an internationally recognized expert on attention-deficit hyperactivity disorder (ADHD) and has dedicated his career to research into this disorder. Currently, he is a clinical professor of psychiatry at the Virginia Treatment Center for Children and Virginia Commonwealth University Medical Center and editor of The ADHD Report.
Having published 23 books, 75 book chapters, and over 198 papers, Russell is passionate about dispelling common misconceptions and educating the world about the science of this disorder. We asked Professor Barkley about his opinions on what remains a divided area of neuroscience research via email. His responses are below.
Tiffany Quinn (TQ): It feels very much like there has been a rise in the prevalence of ADHD, what is responsible for this?
RB: There has not been much if any rise in true prevalence as demonstrated in research studies. However, certain government agencies, like our Center for Disease Control, have conducted studies using very weak methods (one question) yet report to the media about the marked prevalence of ADHD (as high as 10-12% in some age groups). The actual prevalence remains between 5-7% and that is true worldwide. Differences in studies or across countries are entirely due to using different methods to assess ADHD. A very small rise in ADHD may have occurred back in the 1970s due to the increasing availability of neonatal intensive care units that saved more premature and otherwise high risk babies, some of whom would go on to have ADHD rather than cerebral palsy, intellectual disability, or even death but who now would have milder disorders like ADHD and learning/language disorders. Another slight rise may have occurred secondary to women (and men) in developed countries delaying the birth of their first children for longer than in prior generations, say into their 30s. Such delays increase the risk for genetic mutations to occur in their sperm and egg and these mutations may be more likely to occur in genes related to autism spectrum disorder and ADHD. Older parents, particularly men, therefore posed a possible increase in prevalence for ADHD (perhaps 10% more than usual) and ASD (about 25% more than before).
TQ: You describe ADHD as a disorder of executive functioning however there is still a lot of confusion about how exactly executive functioning relates to ADHD. Could you talk us through your model and how you came to understand ADHD in this way?
RB: The model is complex but essentially says that ADHD is not just an attention disorder but one of the brain’s executive system. That system is comprised of about 7 different mental abilities or modules that develop slowly taking about 30 years to complete and that develop in a sequence. I view each of them as a form of self-directed actions or behavior that we use to change our behavior from what it would automatically have been. And we do that to change our future, that is the likelihood of some delayed consequence occurring. So each executive function (EF) is a form of self-control. By adulthood, we have 7 (or more) that interact to produce a set of mind tools, like Swiss Army Knife, of self-regulation. We use them to plan for, anticipate and prepare for our future, or at least the future we are planning for. All plans for the future are hypothetical because the actual world is not obligated to follow our version of the anticipated future.
The 7 EFs are: (1) self-awareness, or self-directed attention; (2) inhibition, or self-restraint; (3) nonverbal working memory, or visual imagery and other forms of sensing to ourself; (4) verbal working memory, or self-speech such as your mind’s voice; (5) emotional self-regulation; (6) self-motivation; and (7) planning and problem-solving, or mental play.
I believe that ADHD disrupts all of these to varying degrees across individuals and this results in their massive problems with self-regulation.
TQ: What are some of the key biological factors underpinning ADHD and how do they relate to the key symptoms of the disorder?
RB: ADHD is due to multiple factors but they can be simplified as genetics and non-shared or unique environmental factors (events that happen to just one children the family), particularly biological hazards or risks. The two can certainly interact with each other. Evidence suggests that about 65% of ADHD is due to genetic factors, such as inheritance of ADHD risk genes. But as I noted above, it can also arise from new mutations in a child occurring in the genes related to regions of the brain that create ADHD symptoms. These mutations may not be present in their parent’s DNA, except perhaps in their eggs and sperm. There can also be interactions of the ADHD risk genes with environmental events, especially during pregnancy. These include exposure to alcohol, tobacco smoke, infections, toxins, and also premature birth as well as birth complications. These are likely to disrupt the development of the executive brain and thus increase risk for ADHD. Even if the child does not carry ADHD risk genes, these factors alone might account for the ADHD through their injury to brain development. We think this accounts for about 25% of ADHD. And then about 5-10% of ADHD arises from exposure to hazards after birth, such as lead, other toxins, brain trauma, or other processes like strokes, tumors, etc., that can disrupt brain development postnatally.
TQ: ADHD is considered one of the top 3 neurological disorders in psychiatry. Despite this, there is still a lot of misunderstanding surrounding the reality and severity of ADHD. Why do you think this is the case?
RB: For several reasons. First, the public has been taught for more than a century via theories of psychological development such as that of Freud and his psychoanalysis, Watson and Skinner and their behaviorism, as well as Marx and Engels and their theory of communism, all of which argue that a large share of human behavior and development is a consequence of the environment. All are forms of utopian thinking in arguing that we can design society to make for better humans as if humans were blank slates. We now know that such theories focusing solely on environment are wrong; there is an interplay of nature and nurture here and the nature portion of it can no longer be ignored. Yet the public continues to believe, long after science has disproven it, that most or all behavioral problems of children must be due to the environment in which they are raised and their parenting in particular. So when people see problems in children like ADHD, their first reaction is that its due to poor parenting, especially by mothers. It will take a long time for the public to come to match its own assumptions about behavior with what science has revealed, just as there exists a mismatch between public views of evolution and the science of evolution.
Second, fringe political and religious organizations have periodically succeeded in getting the press to report stories that ADHD is a myth or, if it exists at all, is due to poor parenting, and that it is way over-diagnosed and over-treated, none of which is true. But the media covers such accusations for their sensational bias and so the public is exposed to such ideas even though they have no scientific standing.
TQ: In 2013, the University of Exeter reported a gap between the diagnosis of ADHD in the US vs the UK. Why do you think that was the case and do you think this gap still exists?
RB: Part of this difference is that the UK still adhere to the ICD-10 diagnostic criteria and the term Hyperkinetic Disorder of Childhood, which are more restrictive than the DSM-5 criteria in the US. When the same criteria are used in each country we have about the same actual rate of ADHD in the population. There was a tendency in the UK to prefer to label those with ADHD as having conduct problems or Conduct Disorder instead. That may be changing now.
TQ: Is there a distinction between childhood and adult ADHD?
RB: Not really. ADHD can have its onset at anytime during development, meaning up to 18-24 years of age, roughly. The fact that DSM-5 says the onset has to be 12 should largely be ignored. While most cases do report an onset before this, about 7-10% of children and 25-35% of adults will report an onset after this age yet still meet all other criteria for the disorder and thus are frankly ADHD. Because ADHD is a dimension in the population, not a category, there are cases of subthreshold ADHD in children (those who fall short of DSM or ICD criteria by 1-2 symptoms) who will, over time, then go on to develop enough new symptoms to get diagnosed later in life. So most were ADHD all along but not able to meet full diagnostic criteria until later in adolescence or young adulthood. A problem with all this research is that children, teens, and young adults (and their parents) are grossly unreliable in reporting an age of onset for ADHD (or any disorder). So someone can say it developed at age 18-19 (adult onset) when in fact it developed 5-7 years earlier (childhood onset). That is why clinicians are told to give little heed to the age of onset criterion for diagnosis – its simply unreliable.
TQ: There is no cure for ADHD, but treatments exist which can help to manage it. Which treatment(s) do you recommend to patients, especially children?
RB: Some people with ADHD do remit or grow out of it. This could be anywhere from 14-35% depending on how strict a definition of recovery or normalization one uses. But it does happen. Recent studies show that such cases show more development in the brain regions that are related to ADHD than in those whose ADHD persists to adulthood such that the remitters have brains that are closer to normal in size and connectivity. But for the remainder there is no known cure. We recommend a package of treatments that include (1) thorough diagnosis, (2) education about the disorder, (3) medications, (4) behavior modification methods such as those used in parent training, classroom management, and adult cognitive behavioral therapy, and (5) accommodations, or physical changes to the environment that reduce impairments. An example of the latter for an adult is changing your workspace so it is better organized, with less distractions, and making yourself accountable to others frequently for the work you agree to produce. For a child it might be having the child sit closer to the teacher’s teaching area so she can monitor the child more often and breaking down the assigned work into smaller quotas with frequent breaks.
TQ: There has been some debate surrounding the use of psychostimulants to treat children with ADHD, owing to suggestions that doctors are wrongly using behavioral, rather than cognitive performance to prescribe these drugs. What are your thoughts on this?
RB: I disagree. These remarks usually imply that if you judge a child’s drug response by reports of their behavior, such as on rating scales, you may choose a higher dose than had you used some lab test of attention or inhibition to adjust the dose. While a study 30 years ago implied this to be the case, subsequent research shows that such tests are the least sensitive to medication effects compared to parent and teacher ratings and do not correlate with observations of the child in the real world. So the problem is with the tests not the behavior ratings. One is always better adjusting doses based on parent and teacher reports and not on some arcane lab or clinic test.
TQ: What excites you the most about the future of ADHD research and why?
RB: The advances being made in genetics offer the opportunity to discover new and perhaps better medications. Once the genes are identified and their role in brain development and regulation is known this will suggest new medications that might help better. Of course such advances may at some point help with better diagnosis and with choosing treatments but the field of genetics is not yet far enough along to permit that.
Advances in neuro-imaging are resulting from ever greater resolution of brain structures and their functional connectivity giving us a much clearer picture of how ADHD arises and how treatments work. Perhaps someday these methods can also assist with diagnosis, but they can not do so just yet.
Research on psychological treatments is not advancing so quickly as is that involving medications. But some promising developments are in social skills training and the work of Amori Mikami, Ph.D. from the University of British Columbia in Vancouver. Also, the latest work on cognitive behavioral therapies focusing on the executive function deficits of adults with ADHD offers a new treatment for adults, such as the work of Mary Solanto, Ph.D. in New York and that of J. Russell Ramsay, Ph.D. in Philadelphia, and Laura Knouse, Ph.D., in Richmond, VA. Adult ADHD Coaching, the positive impact of physical exercise, and possibly some usefulness for mindfulness meditation for stress reduction all have shown early promise but need more research to be definitive.
Russell Barkley was speaking to Tiffany Quinn, Custom Content Coordinator at Technology Networks.