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April 7, 2021
There is a growing interest (and controversy) in 'adult-onset ADHD. No current diagnostic system allows for the diagnosis of ADHD in adulthood, yet clinicians sometimes face adults who meet all criteria for ADHD, except for age at onset. Although many of these clinically referred adult-onset cases may reflect poor recall, several recent longitudinal population studies have claimed to detect cases of adult-onset ADHD that showed no signs of ADHD as a youth (Agnew-Blais, Polanczyk et al. 2016, Caye, Rocha, et al. 2016). They conclude, not only that ADHD can onset in adulthood, but that childhood-onset and adult-onset ADHD may be distinct syndromes(Moffitt, Houts, et al. 2015)
In each study, the prevalence of adult-onset ADHD was much larger than the prevalence of childhood-onset adult ADHD). These estimates should be viewed with caution. The adults in two of the studies were 18-19 years old. That is too small a slice of adulthood to draw firm conclusions. As discussed elsewhere (Faraone and Biederman 2016), the claims for adult-onset ADHD are all based on population as opposed to clinical studies.
Population studies are plagued by the "false positive paradox", which states that, even when false positive rates are low, many or even most diagnoses in a population study can be false.
Another problem is that the false positive rate is sensitive to the method of diagnosis. The child diagnoses in the studies claiming the existence of adult-onset ADHDused reports from parents and/or teachers but the adult diagnoses were based on self-report. Self-reports of ADHD in adults are less reliable than informant reports, which raises concerns about measurement error. Another longitudinal study found that current symptoms of ADHD were under-reported by adults who had had ADHD in childhood and over-reported by adults who did not have ADHD in childhood(Sibley, Pelham, et al. 2012). These issues strongly suggest that the studies claiming the existence of adult-onset ADHD underestimated the prevalence of persistent ADHD and overestimated the prevalence of adult-onset ADHD. Thus, we cannot yet accept the conclusion that most adults referred to clinicians with ADHD symptoms will not have a history of ADHD in youth.
The new papers conclude that child and adult ADHD are "distinct syndromes", "that adult ADHD is more complex than a straightforward continuation of the childhood disorder" and that adult ADHD is "not a neurodevelopmental disorder". These conclusions are provocative, suggesting a paradigm shift in how we view adulthood and childhood ADHD. Yet they seem premature. In these studies, people were categorized as adult-onset ADHD if full-threshold add had not been diagnosed in childhood. Yet, in all of these population studies, there was substantial evidence that the adult-onset cases were not neurotypical in adulthood (Faraone and Biederman 2016). Notably, in a study of referred cases, one-third of late adolescent and adult-onset cases had childhood histories of ODD, CD, and school failure(Chandra, Biederman, et al. 2016). Thus, many of the "adult onsets" of ADHD appear to have had neurodevelopmental roots.
Looking through a more parsimonious lens, Faraone and Biederman(2016)proposed that the putative cases of adult-onset ADHD reflect the existence of subthreshold childhood ADHD that emerges with full threshold diagnostic criteria in adulthood. Other work shows that subthreshold ADHD in childhood predicts onsets of full-threshold ADHD in adolescence(Lecendreux, Konofal, et al. 2015). Why is onset delayed in subthreshold cases? One possibility is that intellectual and social supports help subthreshold ADHD youth compensate in early life, with decompensation occurring when supports are removed in adulthood or the challenges of life increase. A related possibility is that the subthreshold cases are at the lower end of a dimensional liability spectrum that indexes risk for onset of ADHD symptoms and impairments. This is consistent with the idea that ADHD is an extreme form of a dimensional trait, which is supported by twin and molecular genetic studies(Larsson, Anckarsater, et al. 2012, Lee, Ripke, et al. 2013). These data suggest that disorders emerge when risk factors accumulate over time to exceed a threshold. Those with lower levels of risk at birth will take longer to accumulate sufficient risk factors and longer to onset.
In conclusion, it is premature to accept the idea that there exists an adult-onset form of ADHD that does not have its roots in neurodevelopment and is not expressed in childhood. It is, however, the right time to carefully study apparent cases of adult-onset ADHD to test the idea that they are late manifestations of a subthreshold childhood condition.
Agnew-Blais, J. C., G.V. Polanczyk, A. Danese, J. Wertz, T. E. Moffitt and L. Arseneault (2016)."Persistence, Remission and Emergence of ADHD in Young Adulthood:Resultsfrom a Longitudinal, Prospective Population-Based Cohort." JAMA.Caye, A., T. B.-M. Rocha, L. Luciana Anselmi, J. Murray, A. M.B. Menezes, F. C. Barros, H. Gonçalves, F. Wehrmeister, C. M. Jensen, H.-C.Steinhausen, J. M. Swanson, C. Kieling and L. A. Rohde (2016). "ADHD doesnot always begin in childhood: E 1 vidence from a large birth cohort." JAMA.
Chandra, S., J. Biederman and S. V. Faraone (2016)."Assessing the Validity of the Ageat Onset Criterion for Diagnosing ADHD in DSM-5." J Atten Disord.
Faraone, S. V. and J. Biederman (2016). "CanAttention-Deficit/Hyperactivity Disorder Onset Occur in Adulthood?" JAMAPsychiatry.
Larsson, H., H. Anckarsater, M. Rastam, Z. Chang and P.Lichtenstein (2012). "Childhood attention-deficit hyperactivity disorderas an extreme of a continuous trait: a quantitative genetic study of 8,500 twinpairs." J Child Psychol Psychiatry53(1): 73-80.
Lecendreux, M., E. Konofal, S. Cortese and S. V. Faraone(2015). "A 4-year follow-up of attention-deficit/hyperactivity disorder ina population sample." J Clin Psychiatry76(6): 712-719.
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Moffitt, T. E., R. Houts, P. Asherson, D. W. Belsky, D. L.Corcoran, M. Hammerle, H. Harrington, S. Hogan, M. H. Meier, G. V. Polanczyk,R. Poulton, S. Ramrakha, K. Sugden, B. Williams, L. A. Rohde and A. Caspi(2015). "Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder?Evidence From a Four-Decade Longitudinal Cohort Study." Am J Psychiatry:appiajp201514101266.
Sibley, M. H., W. E. Pelham, B.S. Molina, E. M. Gnagy, J. G. Waxmonsky, D. A. Waschbusch, K. J. Derefinko, B.T. Wymbs, A. C. Garefino, D. E. Babinski and A. B. Kuriyan (2012). "Whendiagnosing ADHD in young adults emphasize informant reports, DSM items, and impairment."J Consult Clin Psychol80(6):1052-1061.
Executive function impairment is a key feature of ADHD, with its severity linked to the intensity of ADHD symptoms. Executive function involves managing complex cognitive tasks for organized behavior and includes three main areas: inhibitory control (suppressing impulsive actions), working memory (holding information briefly), and cognitive flexibility (switching between different mental tasks). Improving executive functions is a critical objective in the management of ADHD.
Recent studies show that exercise interventions can enhance executive function in individuals with ADHD. Unlike traditional medications, which are costly and may cause side effects such as headaches, nausea, or growth issues, exercise can be incorporated into daily routines of children and adolescents without negative reactions.
Some studies report that aerobic exercise does not significantly improve executive function. However, most past reviews of aerobic exercise effects on executive function have focused on people without ADHD, with few examining interventions for children or adolescents with ADHD.
The Study:
A Chinese and South Korean study team conducted a systematic search of the peer-reviewed published literature to perform meta-analyses on randomized controlled trials (RCTs) specifically focused on aerobic exercise interventions for children and adolescents with ADHD.
All studies included were randomized controlled trials involving participants aged 6 to 18 years who had been clinically diagnosed with ADHD. The interventions consisted of various forms of aerobic exercise, while the control groups engaged in either non-exercise activities or daily routines. Each study was required to report at least one outcome measure with usable data for calculating the effect size on executive functioning.
The Results:
Meta-analysis of fifteen RCTs combining 653 children and adolescents with ADHD reported a medium to large effect size improvement in inhibitory control. There was no sign of publication bias, but wide heterogeneity (variation) in outcomes among studies.
Six to eight weeks of aerobic exercise produced modest improvements, with much greater gains seen after twelve weeks. Hour-long sessions were as effective as longer ones. Moderate intensity exercise proved more beneficial than vigorous intensity.
Meta-analysis of eight RCTs combining 399 children and adolescents with ADHD produced a medium effect size improvement in working memory. There was no sign of publication bias, and heterogeneity was moderate.
Once again, six to eight weeks of aerobic exercise produced modest improvements, with much greater gains seen after twelve weeks. Hour-long sessions were as effective as longer ones. But in this case moderate-to-vigorous intensity yielded the best results.
Meta-analysis of ten RCTs combining 443 children and adolescents with ADHD was associated with a medium to large effect size improvement in cognitive flexibility. There was no sign of either publication bias or heterogeneity. Neither the length of treatment, session time, or intensity affected the outcome.
The Take-Away:
The team concluded, “Our study indicates that aerobic exercise interventions have a positive impact with a moderate effect size on inhibitory control, working memory, and cognitive flexibility in children and adolescents with ADHD. However, the effectiveness of the intervention is influenced by factors such as the intervention period, frequency, session durations, intensity, and the choice between acute or chronic exercise. Specifically, chronic aerobic exercise interventions lasting 12 weeks or longer, with a frequency of 3 to 5 sessions per week, session durations of 60 min or more, and intensities that are moderate or moderate-to-vigorous, have the greatest overall effect… caution should be exercised when interpreting these findings due to the significant heterogeneity in inhibitory control and working memory.”
Vitamins play important roles in metabolism, immune regulation, and neurodevelopment. Recent studies show that deficiencies in vitamins like D, B6, B12, and folate are common in people with ADHD and ASD (autism spectrum disorder), and are associated with behavioral, cognitive, and brain development issues.
The Study:
A study team based in China has just performed a systematic search of the peer-reviewed medical literature to perform meta-analyses of clinical trials exploring vitamin interventions in the treatment of ADHD and ASD.
ADHD trials included participants with an official diagnosis. The primary intervention was vitamin supplements, while other treatments, including medications, remained unchanged or were excluded during the study period. ADHD outcomes included measurable changes in ADHD symptoms using validated rating scales and executive function measures.
Eligible studies included standard or sham control groups, crossover, parallel, or other clinical trial designs. In crossover studies, only first-phase data were analyzed to prevent carryover effects.
Ten trials with 852 participants met the standards, but meta-analysis showed no significant results. The outcomes varied widely, suggesting a need to distinguish among vitamins.
Results:
Of the five trials involving 347 participants that specifically evaluated vitamin D supplementation, results indicated a large effect size improvement in ADHD symptoms and executive function measures. The other five studies did not show any observable improvement.
Key limitations include:
The team concluded, “This meta-analysis supports the use of vitamin supplementation as a promising adjunctive treatment for ASD and ADHD. Vitamin B showed greater benefits in improving symptoms of ASD, while vitamin D was more effective in managing ADHD-related behaviors. These findings suggest that specific vitamins may target disorder-specific symptoms. Despite limitations such as the lack of trials on other vitamins and limited understanding of underlying mechanisms, vitamin therapy remains a low-cost, accessible option.”
An important limitation of this work is that the positive results for vitamin D were due to two studies from Iran. So far, no positive study has emerged from a non-Iranian study.
Interpretation:
The vitamin D findings are intriguing and could be important if replicated outside of Iran. Since supplementation is already widely recommended to those with limited sunlight exposure, clinicians may want to consider monitoring their patients’ vitamin D intake, especially in the winter months. It should be noted, however, that due to the limitations of this study, the results are by no means conclusive, and vitamin D should not be taken as a stand-alone treatment for ADHD.
Claims-based real-world data can reveal population-level trends in health among people with neurodevelopmental disorders. This new study examined the prevalence, demographics, and chronic comorbidities of adults and of children and adolescents with ADHD in a large national health plan. It also compared healthcare use and costs between those with and without ADHD.
A research team in the United States conducted an observational cohort study using claims data from more than 1.9 million adults and nearly 500,000 children and adolescents, comparing individuals diagnosed with ADHD to those without the diagnosis.
ADHD was diagnosed in 4% of adults and in 5% of children and adolescents.
Comorbidities By The Numbers:
Disruptive childhood disorders are behavioral problems marked by ongoing defiance, uncooperativeness, and aggression that affect a child's daily life and relationships. The main types, oppositional defiant disorder (ODD) and conduct disorder (CD), involve persistent anger and argumentativeness in ODD, and more severe actions like aggression, cruelty, and criminal behavior in CD. Without treatment, these common childhood disorders can continue into adulthood and raise the risks of substance use, violence, incarceration, and early death.
Disruptive childhood disorders were twenty times more frequent among children and adolescents with ADHD than among those without ADHD diagnosis, and fifteen times more frequent among adults with ADHD.
Bipolar disorder was twelve times more common among children and adolescents with ADHD than those without ADHD, and seven times more common among adults with ADHD.
Schizophrenia was eleven times more prevalent among children and adolescents with ADHD than those without ADHD, and three-and-a-half times more common among adults with ADHD.
Anxiety was nine times more frequent among children and adolescents with ADHD than among those without ADHD diagnosis, and more than five times more frequent among adults with ADHD.
Depression was eight times more common among children and adolescents with ADHD than those without ADHD, and more than five times more common among adults with ADHD.
Suicidal ideation was eight times more prevalent, and suicide attempt seven times more prevalent, among children and adolescents with ADHD than those without ADHD. Both suicidal ideation and suicide attempt were five times more common among adults with ADHD.
Gender dysphoria was almost six times more frequent among children and adolescents with ADHD than among those without ADHD diagnosis, and five times more frequent among adults with ADHD.
Eating disorders were over four times more common among children and adolescents with ADHD than those without ADHD, and five times more common among adults with ADHD.
Substance-related disorders were over six times more prevalent, and alcohol use disorder was six times more prevalent among children and adolescents with ADHD than those without ADHD, and four and three times more prevalent among adults with ADHD.
Increased Costs of Medical Care:
These comorbidities and ADHD led to higher medical costs. Children and adolescents with ADHD spent $610 more annually on healthcare than those without, while adults with ADHD had $1,684 higher average yearly expenditures than non-ADHD adults.
The Take-Away:
This large claims-based analysis of a national commercial insurer found ADHD diagnoses in roughly 4% of adults and 5% of children. It documented substantially higher rates of co-occurring behavioral-health conditions and markedly greater healthcare utilization and expenditures among those with ADHD. The authors report increased odds for several co-occurring diagnoses, as well as higher per-member-per-month (PMPM) spending and per-thousand-per-month (PTPM) utilization, largely driven by greater use of behavioral health services.
Importantly, these results come from cross-sectional, claims data within a commercially insured population: they describe associations, not causal relationships, and may not generalize to uninsured, publicly insured, or otherwise different populations. These findings, therefore, warrant cautious interpretation and highlight the need for longitudinal and more representative studies to clarify drivers of the increased burden and to inform care and policy.
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