Cookie Preferences
By clicking, you agree to store cookies on your device to enhance navigation, analyze usage, and support marketing. More Info
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
July 4, 2021
Our genes are very important for the development of mental disorders-including ADHD, where genetic factors capture up to 75% of the risk. Until now, the search for these genes had yet to deliver clear results. In the 1990s, many of us were searching for genes that increased the risk for ADHD because we know from twin studies that ADHD had a robust genetic component. Because I realized that solving this problem required many DNA samples from people with and without ADHD, I created the ADHD Molecular Genetics Network, funded by the US NIMH. We later joined forces with the Psychiatric Genomics Consortium (PTC) and the Danish psych group, which had access to many samples.
The result is a study of over 20,000 people with ADHD and 35,000 who do not suffer from it - finding twelve locations (loci) where people with a particular genetic variant have an increased risk of ADHD compared to those who do not have the variant. The results of the study have just been published in the scientific journal Nature Genetics, https://www.nature.com/articles/s41588-018-0269-7.
These genetic discoveries provide new insights into the biology behind developing ADHD. For example, some genes have significance for how brain cells communicate with each other, while others are important for cognitive functions such as language and learning.
Our study used the genome-wide association study (GWAS)methodology because it allowed us to discover genetic loci anywhere on the genome. The method assays DNA variants throughout the genome and determines which variants are more common among ADHDvs. control participants. It also allowed for the discovery of loci having very small effects. That feature was essential because prior work suggested that, except for very rare cases, ADHD risk loci would individually have small effects.
The main findings are:
A) we found 12 loci on the genome that we can be certain harbor DNA risk variants for ADHD. None of these loci were traditional candidate genes' for ADHD, i.e., genes involved in regulating neurotransmission systems that are affected by ADHD medications. Instead, these genes seem to be involved in the development of brain circuits.
B) we found a significant polygenic etiology in our data, which means that there must be many loci(perhaps thousands) having variants that increase the risk for ADHD. We will need to collect a much larger sample to find out which specific loci are involved;
We also compared the new results with those from a genetic study of continuous measures of ADHD symptoms in the general population. We found that the same genetic variants that give rise to an ADHD diagnosis also affect inattention and impulsivity in the general population. This supports prior clinical research suggesting that, like hypertension and hypercholesteremia, ADHD is a continuous trait in the population. These genetic data now show that the genetic susceptibility to ADHD is also a quantitative trait comprised of many, perhaps thousands, of DNA variants
The study also examined the genetic overlap with other disorders and traits in analyses that ask the questions: Do genetic risk variants for ADHD increase or decrease the likelihood a person will express other traits and disorders. These analyses found a strong negative genetic correlation between ADHD and education. This tells us that many of the genetic variants which increase the risk for ADHD also make it more likely that a person will perform poorly in educational settings. The study also found a positive correlation between ADHD and obesity, increased BMI, and type-2 diabetes, which is to say that variants that increase the risk of ADHD also increase the risk of overweight and type-2 diabetes in the population. This work has laid the foundation for future work that will clarify how genetic risks combine with environmental risks to cause ADHD. When the pieces of that puzzle come together, researchers will be able to improve the diagnosis and treatment of ADHD.
For years, a persistent concern has shadowed the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD): Does the medication eventually stop working? Patients often report that their symptoms seem to return despite consistent use, leading to "dose escalation" or "medication holidays." A new systematic review from Sam Cortese’s team published in CNS Drugs finally puts these concerns to the test by synthesizing decades of empirical research.
Before diving into the findings, you must understand two often-confused phenomena:
The review analyzed 17 studies covering over 10,000 individuals, and the results provide a much-needed reality check for the clinical community.
The researchers found preliminary evidence that acute tolerance (tachyphylaxis) can occur within a 24-hour window.
The most important finding is that tolerance does not commonly develop to the therapeutic effects of ADHD medication in the long term. In one landmark study following children for up to 10 years, only 2.7% of participants lost their response to methylphenidate without a clear external explanation. Doses, when adjusted for natural body growth, remained remarkably stable over years of treatment.
Consistent with the lack of therapeutic tolerance, the body does not become tolerant to the physical side effects of stimulants. Increases in heart rate and blood pressure typically persist for as long as the medication is taken. This underscores why clinicians must continue monitoring cardiovascular health throughout the entire duration of treatment.
If it’s Not Tolerance, What Is It?
If "tolerance" isn't real, why do some patients feel their medication is failing? The review suggests clinicians look at these alternative explanations:
Why This Matters
These results provide clinicians the confidence to tell patients that their medication is unlikely to "wear out" permanently. Rather than immediately increasing a dose when symptoms flare, the first step should be a "clinical deep dive" into the patient's lifestyle, stress levels, and adherence.
For researchers, the review highlights a major gap: most existing studies are small, dated, or of low quality. There is a dire need for robust, longitudinal studies that track both the brain's response and the patient's environment over several years.
For people with ADHD, while your body might get "used to" the initial "buzz" of a stimulant within hours, its ability to help you focus and manage your life remains remarkably durable over the years.
The Background:
Concerns remain about how ADHD and methylphenidate (MPH) use might affect children's health and growth, and especially how it may affect their adult height. While some studies suggest disrupted growth and a possible biological mechanism, the impact of ADHD prevalence and MPH use is still unclear. Children with ADHD may develop unhealthy habits – irregular eating, low physical activity, and poor sleep – that can contribute to obesity and reduced height. MPH’s appetite-suppressing effect can lead to skipped meals or overeating. Since growth hormone is mainly released during deep sleep, chronic sleep deprivation could plausibly slow growth and impair height development; however, a clear link between ADHD, MPH use, overweight, and shorter stature has never been firmly established.
The Study:
South Korea has a single payer health insurance system that covers more than 97% of its population. A Korean research team used the National Health Insurance Service database to perform a nationwide population study to explore this topic further.
The study involved 34,850 children, of whom 12,866 were diagnosed with ADHD. Of these children, 6,816 (53%) had received methylphenidate treatment, while 6,050 (47%) had not. Each patient with ADHD was precisely matched 1:1 by age, sex, and income level to a control participant without ADHD. The sex ratio was comparable in all groups.The team used Body Mass Index (BMI) as an indicator of overweight and obesity.
The Results:
The researchers found that being diagnosed with ADHD was associated with 50% greater odds of being overweight or obese as young adults, and over 70% greater odds of severe obesity (BMI > 30) compared to matched non-ADHD controls, regardless of whether or not they were medicated.
Those diagnosed with ADHD, but not on methylphenidate, had 40% greater odds of being overweight or obese, and over 55% greater odds of becoming severely obese, relative to matched non-ADHD controls.
Methylphenidate users had 60% greater odds of being overweight or obese, and over 85% greater odds of becoming severely obese, relative to matched non-ADHD controls.
There were signs of a dose-response effect. Less than a year’s exposure to methylphenidate was associated with roughly 75% greater odds of becoming severely obese, whereas exposure over a year or more raised the odds 2.3-fold, relative to matched non-ADHD controls. Using MPH increased the prevalence of overweight from 43.2% to 46.5%, with a greater prevalence among those using MPH for more than one year (50.5%).
It is important to note that most of this effect was from ADHD itself, with methylphenidate only assuming a predominant role in severe obesity among those with longer-term exposure to the medicine.
As for height, children with ADHD were no more likely to be short of stature than matched non-ADHD controls. Being prescribed methylphenidate was associated with slightly greater odds (7%) of being short of stature, but there was no dose-response relationship.
Conclusion:
The team concluded, “patients with ADHD, particularly those treated with MPH, had a higher BMI and shorter height at adulthood than individuals without ADHD. Although the observed height difference was clinically small in both sexes and age groups, the findings suggest that long-term MPH exposure may be associated with growth and body composition, highlighting the need for regular monitoring of growth.” They also point out that “Despite these findings, the clinical relevance should be interpreted with caution. In our cohort, the mean difference in height was less than 1 cm (eg, maximum −0.6 cm in females) below commonly accepted thresholds for clinical significance.” Likewise, increases in overweight/BMI were small.
One problem with interpreting the BMI/obesity results is that some of the genetic variants that cause ADHD also cause obesity. If that genetic load increases with severity of ADHD than the results from this study are confounded because those with more severe ADHD are more likely to be treated than those with less severe ADHD.
Due to these small effects along with the many study limitations noted by the authors, these results should be considered alongside the well-established benefits of methylphenidate treatment.
What do we mean by expert? In simple terms, an expert possesses in-depth knowledge and specialized training in a particular field. In order to be considered an expert in any field, a person must have both deep knowledge of and competence in their specific area of expertise. Experts have a background that includes education, research, and experience. In the world of mental health and psychology, this typically means formal credentials (a PhD, MD, etc) in addition to years of study, peer-reviewed publications, and/or extensive clinical experience.
Experts are recognized by their peers (and often by the public) as reliable authorities on a specific topic. Experts usually don’t make big claims without evidence; instead, they cite studies and speak cautiously about what the evidence shows.
Tip: Those looking for likes and clicks will often speak in absolutes (e.g., “refined sugar makes your ADHD worse, but the Keto Diet will eliminate ADHD symptoms”) while experts will use language that emphasizes evidence (e.g., “research has proven that there is no ‘ADHD Diet’, but some evidence has suggested that certain individuals with ADHD may benefit from such dietary interventions as limiting food coloring or increasing omega fatty acids.”)
Social media has created an incredible opportunity for those with ADHD to gain access to invaluable resources, including the creation of communities by and for those with ADHD. Many people with ADHD report feeling empowered and less alone by connecting with others online. These online social platforms provide a space for those with ADHD to share their own perspectives and their lived experience with the disorder. Both inside and outside of mental health-related communities, social media is a powerful tool for sharing information, reducing stigma, and helping people find community. When someone posts about their own ADHD challenges or tips, it can reassure others that they’re not the only ones facing these issues. This kind of peer support is valuable and affirming.
It is vital for those consuming this media, however, to remember that user-generated content on social media is not vetted or regulated. Short TikTok or Instagram videos are designed to grab attention, not to teach nuance or cite scientific studies. As it turns out, most popular ADHD posts are misleading or overly simplistic, at best. One analysis of ADHD TikTok videos found that over half were found to be “misleading” by professionals. Because social feeds reinforces what we already believe (the “echo chamber” effect, or confirmation bias), we can easily see only content that seems to confirm our own experiences, beliefs, or fears.
Stories aren’t a substitute for expert guidance.
It’s important to recognize the difference between personal experience and general expertise. Having ADHD makes you an expert on your ADHD, but it does not make you an expert on ADHD for everyone. Personal stories are not scientific facts. Even if someone’s personal journey is true, the same advice or experience may not apply to others. For instance, a strategy that helps one person focus might have no effect– or possibly even a negative effect– on someone else.
Researchers have found that most ADHD content on social media is based on creators’ own experiences, not on systematic research. In one study, almost every TikTok ADHD creator who listed credentials actually just cited their personal story. Worse, about 95% of those videos never noted that their tips might not apply to everyone (journals.plos.org.) In other words, they sound absolute even though they really only reflect one person’s situation. It’s easy to misunderstand the condition if we take those singular experiences as universal facts.
So how can you tell when someone is speaking from expertise rather than personal experience or hearsay? Experienced professionals usually speak cautiously, rather than in absolutes. They tend to say things like “research suggests,” “some studies show,” or “evidence indicates,” rather than claiming something always or never happens. As one health-communication guide puts it, a sign of a trustworthy source is that they do not speak in absolutes; instead, they use qualifiers like “may,” “might,” or refer to specific studies. For example, an expert might say, “Some people with ADHD may have difficulty with organization,” instead of “ADHD people always lose things.”
Real experts also cite evidence. In science and psychology, experts usually share knowledge through peer-reviewed articles, textbooks, or professional conferences – not just social media posts. Reliable health information is typically backed by references to studies published in reputable journals.
If someone makes a claim online, ask: Do they point to research, or is it just their own testimony? This is why it’s wise to prefer content where the author is a recognized authority (like a doctor or researcher) and where references to scientific studies or official guidelines are provided. In fact, advice from sites ending in “.gov”, “.edu”, or “.org” (government, university, or professional organizations) tends to be more reliable than random blogs. When in doubt, look up who wrote the material and whether it cites peer-reviewed research.
When navigating mental health information online, remember these key points:
If you see sweeping statements like “This one habit will predict if you have ADHD” or “Eliminating this one food will cure your ADHD symptoms”--- that’s a red flag. Instead, the hallmark of expert advice is a tone of humility (“evidence suggests,” “it appears that,” etc.), clear references to studies or consensus statements, and an acknowledgment that individual differences exist.
At the same time, we need to acknowledge that community voices are incredibly valuable – they help us feel understood and less alone. The goal is not to dismiss personal stories, but to balance them with facts and evidence-based information. Let lived experience spark questions, but verify important advice with credible sources. Follow trusted organizations (for example, the National Institutes of Health, CDC, or ADHD specialist groups) and mental health professionals who communicate carefully. Use the online ADHD community for support and sharing tips, but remember it’s just one piece of the puzzle.
By being a savvy reader (checking credentials, looking for cited evidence, and spotting overgeneralizations), you can make the most of online ADHD content. In doing so, you give yourself both the empathy of community and the accuracy of real expertise. That way, you’ll be well-equipped to separate helpful insights from hype and to keep learning from both personal stories and science-based experts.
_logo%201.svg)
