Saturday, 29 September 2018

1 in 10 kids: the estimated prevalence of ADHD in the United States in 2016

Credit: Xu et al (2018) JAMA Network Open
"In a nationally representative population, we estimated that the prevalence of diagnosed ADHD [attention-deficit hyperactivity disorder] among US [United States] children and adolescents was 10.2% in 2016."

So said the findings published by Guifeng Xu and colleagues [1] who relied on data derived from the National Health Interview Survey (NHIS) in the United States over the course of two decades (1997-2016). As per an accompanying editorial [2] with the smart title "Paying Attention to Attention-Deficit/Hyperactivity Disorder", the Xu findings "fills an important need" insofar as their plotting a significant increase in the estimated prevalence rate of ADHD. The stats: "the estimated prevalence of ADHD significantly increased during the past 20 years—from 6.1% in 1997-1998 to 10.2% in 2015-2016." The year-on-year percentage figures considered by Xu et al showed a rise almost every year when it came to the [estimated] ADHD prevalence. Such figures are quite distinct from other (point) estimates in other parts of the world (see here).

Of course there are upsides and downsides to the authors' reliance on the NHIS dataset. So: the reliance on "parental reports about psychopathology rather than actual standardized assessments administered face-to-face with parents and/or children by trained evaluators" is one of the main limitations talked about across many different labels (see here). This has to be balanced with the large sample size included in the NHIS initiative and the "high response rate (child response rate of 85.6%-93.3%)." Personally I'm not inclined to believe that significant numbers of parents would provide 'false' answers to questions like: “Has a doctor or health professional ever told you that [the sample child] had attention-deficit/hyperactivity disorder (ADHD) or attention-deficit disorder (ADD)?” or “Does [the sample child] currently have attention-deficit/hyperactivity disorder (ADHD) or attention-deficit disorder (ADD)?” but ho-hum.

Then to the million dollar question: why has the estimated ADHD prevalence rate increased so dramatically across a relatively short period of time? Well, some well-worn explanations also seen with regards to the autism prevalence statistics (see here) have been banded around. So: "Nonetiologic factors may partly explain the apparent increase in the prevalence of diagnosed ADHD in this study" such as physician "sensitivity" to a diagnosis of ADHD, alongside the changes in ADHD diagnostic criteria already talked about in the peer-reviewed domain (see here). The issue of screening and diagnosis among non-white groups and their accessibility to said screening/diagnostic services is also discussed (something else that cropped up with the recent autism stats in mind too). And since I've just mentioned autism, it's also likely that the increasing recognition that ADHD is part of the clinical picture for quite a few on the autism spectrum (see here) probably contributes to the increase too.

But then there is the idea that the increase may also be - in part - reflective of a real increase too (see here). There are lots of possible candidates that may be contributory (see here and see here for examples) covering a multitude of genetic and non-genetic factors appearing during the nine months that makes us and beyond. As with any other developmental label and the reason(s) it comes about, there are going to be a multitude of potentially important factors to consider that may be quite individual. One thing is evident however, for whatever reason(s), the numbers are only heading in one direction...

A final question: what can be done to improve the life outcomes of those diagnosed with ADHD in ever-increasing numbers? I mention that question in the context that ADHD seems to elevate the risk of various adverse life events occurring (see here and see here and see here for examples) as well as being a potential 'driver' for other psychopathology appearing too (see here). In this context, we are already beginning to appreciate the benefits of certain types of intervention (see here) as well as the potential value of various other intervention options that are not yet considered 'mainstream' (see here and see here for examples). Further research is required to understand the societal and biological factors linked to a diagnosis of ADHD, and whether further advances in intervention and management can be made as a result, and onward lives (hopefully) enhanced...


[1] Xu G. et al. Twenty-Year Trends in Diagnosed Attention-Deficit/Hyperactivity Disorder Among US Children and Adolescents, 1997-2016. JAMA Network Open. 2018; 1: e181471.

[2] Dickstein DP. Paying Attention to Attention-Deficit/Hyperactivity Disorder. JAMA Newtork Open. 2018; 1: e181504.


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