Currently, in many countries a wide variety of children are being classified as having ADHD and placed on a regimen of consuming psychiatric drugs. Supporters of this trend often cast a disrespectful eye toward their critics while arguing that scientific research supports their position. Meanwhile, equally scientific minded individuals who have looked at the same research come up with a completely different set of conclusions. So, about once a year I take a look at the most current research to see if I can throw some light on this topic.
Last year, for example (see HERE), I reported on a study that suggested that:
Children and adolescents who take medication for attention-deficit hyperactivity disorder (ADHD) show decreased bone density, according to a large cross-sectional study that appeared in the Journal of Pediatric Orthopaedics.
Factors looked at were academic achievement and social functioning. Although the medicated ADHD students didn’t do any better or worse on these measures then the unmedicated ADHD students, they did endure many uncomfortable side effects while they were on the ADHD drugs, such as sleep problems, headaches, stomach aches, and feelings of depression each evening when the drug wore off. Thousands of dollars per child were consumed on purchasing the medications that achieved some modest short term gains but had no lasting positive effects.
How about this year? Are there any new studies that throw light on the ADHD controversy?
The Latest Study
The April 2017 issue of Lancet Psychiatry contains a write-up of a study that looked at the largest data set to date to see if people who have been labelled as having ADHD had some difference in certain regions of their brains than people who were not labelled (the control group). The sample comprised 1713 participants labelled as having ADHD and 1529 controls from 23 sites with a median age of 14 years (range 4–63 years).
Of the 8 areas of the brain that they looked at using MRI scans, 6 were statistically smaller for the group of ADHD labelled people when compared to the control group, but this statistical difference was only found for the group of children younger than 15. When the study looked at these regions of the brains of adults, there were no statistically significant differences.
The authors claimed that their analysis supports the theory that ADHD is due to a delay in the brain maturing. Finally, they concluded that their study contained important messages for clinicians: “The data from our highly powered analysis confirm that patients with ADHD do have altered brains and therefore that ADHD is a disorder of the brain. This message is clear for clinicians to convey to parents and patients, which can help to reduce the stigma that ADHD is just a label for difficult children and caused by incompetent parenting. We hope this work will contribute to a better understanding of ADHD in the general public” (p. 7).
Media Coverage of the Latest Study
Shortly after the publication of this study, two people with impressive scientific credentials, Michael W. Corrigan, Ed.D. and Robert Whitaker, thoroughly analyzed it, and concluded that the study is very misleading and they are calling for it to be retracted. Their entire analysis, which I highly recommend, is available for free HERE. For my readers, I will summarize a few of its key points.
The authors refute the study’s conclusion that it found that people labelled as having ADHD have smaller brain volumes. Thus they state:
“In this study, the authors pooled together MRI brain-scan data for the 3,242 participants in the study (which had been collected and archived at the 23 sites), and then calculated, for each cohort, mean intracranial volumes and mean volumes of specific brain regions. They reported the differences for each of these comparisons and the “effect size” of the differences. This is the critical aspect of the results to consider and understand: effect sizes reveal the true strength of the findings and how much overlap there is between the individual brain volumes in both groups, and thus establish the likelihood that an individual in the ADHD group has a smaller brain volume than an individual in the control group.
The biggest effect size that was found was .19. This was for differences in the mean volume of a region known as the accumbens for ADHD labelled children under 15 years of age. An effect size of 3, which is the largest effect size one can obtain using this type of statistic, would have suggested that pretty much all of the children in the study that were labelled as having ADHD had a distinctly smaller volume in that region than controls. An effect size of 2 would have suggested a distinctly weaker relationship and that some of the children in the ADHD group did not have smaller volumes than the control group, some in the ADHD group had larger volumes than the control group, and some of the control group had smaller than average volumes in that region and yet showed no signs of ADHD. An effect size of 1 would have indicated even a weaker relationship. The effect size of .19 is less than a fifth the size of 1, that is, about a small an effect size as you can imagine. (To learn more about what an effect size is, access this article by Robert Coe: It’s the effect size, stupid.) The critique summarizes this issue as follows:
“In short, if you just flipped a coin to guess which of the two cohorts the child belonged to, your odds of being right would be nearly the same. The diagnostic value of an MRI brain scan, based on the findings in this study, would be of little more predictive value than the toss of a coin.”
Perhaps the best way to understand this is to look at the individual site data. Thus, the study’s authors reported that the “volumes of the accumbens, amygdala, caudate, hippocampus, putamen, and intracranial volume were smaller in individuals with ADHD compared with controls in the mega-analysis” (p. 1). If this is true, then smaller brain volumes should show up in the data from most, if not all, of the 21 sites that had a control group. But that was not the case.
Here are summaries of individual site results:
- Mean accumbens volumes: At 4 sites, the volume for the ADHD cohort was actually larger than for the control, and at another 6 sites, the mean volumes were basically of equal size.
- Mean amygdala volumes: At 5 sites, the mean volume for the ADHD cohort was larger than for the controls, and of equal size at 4 others.
- Mean caudate volumes: At 5 sites, the mean volume for the ADHD cohort was larger than for the controls, and of equal size at 2 others
- Mean hippocampus volumes: At 7 sites, the volume for the ADHD cohort was larger than for the controls, and of equal size at 4 others.
- Mean putamen volumes: At 5 sites, the volume for the ADHD cohort was larger than for the controls, and of equal size at 1 other.
- Mean intracranial volumes: At 5 sites, the volume for the ADHD cohort was larger than for the controls.
“The problem here is obvious,” says the writers of this critique. “If the authors are claiming that smaller brain regions are a defining ‘abnormality’ of ADHD, then such differences should be consistently found in mean volumes of ADHD cohorts at all sites. The fact that there was such variation in mean volume data is one more reason to see the authors’ conclusions—that smaller brain volumes are a defining characteristic of ADHD—as unsupported by the data.”
The critique goes on to mention a number of other serious problems with this study. For example, in a scientific study we look for possible sources of bias. The critique correctly points out that this study was written by an authors’ group that included many who had close ties to pharmaceutical companies that sell ADHD medications. We can also surmise that some, if not all, of the authors who do not currently have ties to these pharmaceutical companies may hope to land in the future financially rewarding speaking fees sponsored by these companies.
There are many other serious weaknesses with this study that the critique points out, but since it is readily available for free, I’ll end my summary here. My own conclusion is this. The study’s results are highly questionable. Particularly troubling is the suggestion by the study’s authors that their findings will help to reduce stigma. How in the world does telling people that ADHD people have smaller brains help to reduce stigma for that group of people? Moreover, even if we found enough evidence to conclude that there are some differences in the brains of people being labelled ADHD, this would still not lead us to conclude they have a brain disorder. A difference is not automatically a disorder. Having people with different brains can be a wonderful thing. For example, it can mean that some people will prefer to work sitting all day, while others prefer to do work requiring lots of activity. We need both types of people, and other types as well, to enrich our lives.
Some people will enjoy reading this blog by beginning with the first post and then moving forward to the next more recent one; then to the next one; and so on. This permits readers to catch up on some ideas that were presented earlier and to move through all of the ideas in a systematic fashion to develop their emotional intelligence. To begin at the very first post you can click HERE.