The neuroscience of ADHD

Mar 8, 2016 /

Half of the American preschoolers diagnosed with ADHD are given drugs to treat the symptoms. Is that necessary? Is there another way?

Neurobiologist David Anderson is alarmed by the idea of drugging children to treat the symptoms of attention deficit hyperactivity disorder (ADHD). Especially during adolescence, when changing levels of sex hormones and growth hormones are already having a dramatic impact on a teenager’s brain, he questions the long-term use of a drug that promotes a system like dopamine or serotonin. As he puts it: “You can’t take the kid off the drug after puberty and say, ‘Whoops, let’s go back and do puberty without the drug.’” Read on to learn how drugs like Adderall affect the brain — and why Anderson says that drug treatments should be a last resort in children with ADHD.

One in 10 American children is diagnosed with ADHD — but we still don’t understand the disorder. “There’s this traditional view that common brain disorders like ADHD, anxiety and depression are caused by chemical imbalances in the brain, as if the brain were some kind of chemical soup that just needed a little more salt,” says Anderson (TEDxCaltech talk: Your brain is more than a bag of chemicals). Then there’s the emerging view, which is that ADHD and other common brain disorders are “actually disturbances in the neural circuits that mediate emotion, mood and affect.” This distinction matters most when parents, doctors and teachers are evaluating the pros and cons of behavioral, environmental and medical treatment options for a growing child, since current drug treatment options act by globally changing brain chemistry. “Many of the drugs that are taken for conditions like these were discovered by accident, not through an understanding of the underlying physiology of the disorder,” says Anderson. “It was just discovered that they work, and we don’t know how they work really or why they work.”

Just what are the long-term consequences of taking a drug like Adderall for years at a time?

For children with ADHD, medication should be a last resort. The ADHD drug Adderall is a good example to consider. “Adderall is basically amphetamines, and it works by increasing the amount of dopamine that is released into the brain,” says Anderson. The problem is, dopamine doesn’t have a single function, so to say that dopamine is involved in ADHD isn’t saying very much. “There are dopamine fibers in many regions of the brain, and around ten different kinds of dopamine neurons in the brain, and most of those neurons will be affected by amphetamine, and those neurons may be doing many different things.” That’s why a medication like Adderall can have so many side effects. “It’s a little like trying to fix your car by pouring oil over the engine — some of it may dribble into the right place, but a lot of it will do more harm than good.”

Another concern is that the brain reacts to being constantly bathed in this drug, and we know very little about what kind of compensating reactions there are and how they affect brain function in the long term, notes Anderson. In other words, if a child has been taking a drug like Adderall for two years and then stops, their brain is not in the same state that it was in before. “So you’re not just pouring oil over the engine — the engine is actually changing as a consequence of being bathed in engine oil all that time.” If there’s one key message Anderson wants to convey, it’s that “there should be more public pressure on the pharmaceutical industry, and also on our federal funding agencies, to perform and support studies of the long term consequences of treating pre-adolescent and adolescent children with these drugs over periods of years, and to look at what happens as these individuals are taken off the drugs after periods of time.”

There’s a societal issue here, as well as a public policy issue.

Does school-based behavioral therapy need a public policy push? Maybe. The CDC estimates that about half of the American preschoolers diagnosed with ADHD are given drugs to treat the symptoms — and that about 1 in 4 are treated only with medication. Yet the recommended first-line treatment is not medication, but behavioral therapy — and there are a number of other environmental and educational variables that can be adjusted. One of the advantages of drug treatment is that it’s easier for the adults involved, notes Anderson. To go a non-pharmaceutical route? That requires more energy from parents and teachers. If there are five kids in class with ADHD, for example, and four of them are on medication, are teachers willing to modify the classroom environment to meet the needs of the fifth child? If you are an American parent working a blue-collar job, is your employer going to tolerate the fact that you need to leave work an hour early to take your child to therapy? “There’s a societal issue here, as well as a public policy issue,” says Anderson.

What’s next for treatment? “If we want to understand what goes wrong in these disorders, we have to understand how the wiring of the brain and the computational parts of the brain contribute to emotion,” says Anderson. That can lead to more targeted forms of therapy, such as deep brain stimulation. Fortunately, scientists now have ways of measuring the activity of neurons in the brain that nobody even thought of 50 years ago. For example, instead of measuring electrical activity, neuroscientists can now use light to probe the brain. “The thought that we’re going to unravel all of this complexity and come to a quick fix any time soon is overly optimistic,” says Anderson. “But at least we’re getting to know how high is the mountain we’re trying to climb.”

The future of “normal”. One way of looking at what is called ADHD is as part of a spectrum of human behaviors that in the past have been considered part of the normative range. Today, there is a movement to accept extremes in the behavior distribution as “normal” and not as pathological, in the sense of representing a disorder or condition that needs to be treated medically. For Anderson, the main question is simply, what are you willing to live with? “For the environment and the conditions and society and family in which you function on a day to day basis, is this condition adaptive or maladaptive? That’s the key.”