Editor’s Note: This is the cover letter that Michael Corrigan and I sent to Niall Boyce, editor of Lancet Psychiatry, requesting that the journal retract Martine Hoogman’s study of “subcortical brain volumes” in those diagnosed with ADHD.
(Lancet Psychiatry’s response is below.)
Dear Niall Boyce:
As you may know, Mad in America Foundation has published a critique of Martine Hoogman’s study of “subcortical brain volumes” in those diagnosed with ADHD, which was published online by Lancet Psychiatry on February 15. We have also put up a petition calling for its retraction, which has now been signed by more than 800 people, including a number of researchers.
We are writing today to formally request that Lancet Psychiatry retract the study.
While there are many problems with this study, there are two scientific flaws that, in particular, argue for its retraction:
a) Hoogman and her collaborators write, in their abstract, that the “volumes of the accumbens, amygdala, caudate, hippocampus, putamen, and intracranial volume were smaller in individuals with ADHD compared with controls.”
The key phrase here is “individuals”, which was a phrase repeated in the text and in media headlines around the world. This study was said to show that individuals in the ADHD cohort had smaller brain volumes than normal.
As you know, the effect sizes for these five volume comparisons were small. This meant that the data showed that the distribution curves for individual brain volumes mostly overlapped. The fatal scientific flaw here is obvious: You cannot take a small difference in mean volumes from two groups and state that the small difference is characteristic of individuals in the two cohorts, and is thus a distinguishing feature of ADHD. The conclusion is false.
b) The authors state, in the abstract, that they “refute medication effects on brain volume suggested by earlier meta-analyses.”
This is a definitive claim about a controversial issue, particularly since they are touting their study as more compelling than the earlier meta-analyses. But they give no data in the article that supports their claim. They state that there was no significant difference in brain volumes in ADHD patients who never took stimulant medication and those who did at some point, but they don’t provide any comparative data, or tell readers anything meaningful about the medication-naïve and medication-exposed groups.
As such, they make a conclusive statement in the abstract that is unsupported by any supporting data in the text, and that goes against standard principles that govern publication in a scientific journal.
There are other problems with the study that provide reason to question the validity of even the small differences in mean brain volumes of the two groups, many of which we have set forth in our published critique.
We understand that the authors are now stating that the IQ scores they published in the appendix were in error (perhaps they spotted that error after we wrote about IQ scores in our critique and in the petition.) While their correction removes this element as a reason for retraction, the fact that it was misreported in the first place provides reason to question the accuracy of other reported data.
In sum, Lancet Psychiatry published a study that generated misleading media headlines around the world, which have served to misinform the public about what is known about ADHD. This misinformation will be profoundly stigmatizing to children so diagnosed, and cause parents of such children to think of them as having “smaller brains than normal.” As such, this is a case of a scientific journal, by publishing an article with a false conclusion, of “doing harm.” For that reason, we respectfully request that Lancet Psychiatry retract the study, and inform the media of the reasons why this retraction was necessary.
We look forward to your response.
Sincerely,
Michael Corrigan, Ed.D.
Robert Whitaker, Mad in America Foundation
Response from Niall Boyce:
Many thanks for your email, Robert. We will be publishing a set of letters critiquing the paper with an author response online and subsequently in print. I anticipate that the authors will also address these points in their response.
All best wishes—
Niall
