November 19, 2021
Danish health care is universal and free. That means there is very complete data available that covers the entire population. The health registers are linked to other national registers that provide access to socioeconomic information. That offers unusual opportunities to research correlations across an entire national population.
Moreover, the health care system requires a high standard for diagnosis of ADHD - evaluation by specialist doctors or psychiatrists rather than a general practitioner. An exception is when parents seek a diagnosis from a private practicing child psychiatrist, in which case diagnostic registration is not mandatory and data is therefore incomplete.
A trio of Danish researchers used the country' national registers to conduct a nationwide population cohort study to explore the cumulative effects of social disadvantages as risk factors for being diagnosed with ADHD.
They looked at all 632,725 children born in Denmark during the 1990s, of which 23,287 (3.7 percent) either had a registered diagnosis in the Patient Registry or else were undergoing ADHD treatment before age 18. Of these, 12,610 children had a registered ADHD diagnosis and entered medical treatment, 4,049 children had a registered diagnosis with no medical treatment, and 6,628 children entered medical treatment with no registered diagnosis. The latter were presumably diagnosed by private practicing psychiatrists. Adjustments were made for gender, immigrant status, birth characteristics (weight, gestational age), single-parenthood, parent ADHD diagnosis, and the number of children in the household.
The study determined that parental educational attainment had the largest effect on the risk of ADHD. Having parents who completed no more than the minimum compulsory education was associated with a 3.5 percentage point higher risk of getting an ADHD diagnosis. Completing no more than upper secondary education was associated with a 1.3 percent higher risk. But there was a sharp bifurcation in the two alternative components of upper secondary education. Children of parents who completed a vocational track faced a 1.7 percent increase in risk, whereas those whose parents completed a college preparatory track faced a negligible 0.17 percent increase.
Parental unemployment also had a significant effect. Youths whose parents were unemployed most of the year faced a 2.1 percent higher risk of ADHD, whereas those whose parents were unemployed less than half the year faced a 1.3 percent higher risk.
Relative income poverty had a comparable impact. Children of parents in the lowest income quintile faced a 2.3 percent higher risk of ADHD than those of parents in the uppermost income quintile. Those in the second-lowest quintile faced a 1.9 percent higher risk than those in the uppermost quintile; those in the middle quintile a 1.3 percent higher risk, and those in the second-highest quintile a 0.8 percent higher risk.
All three cases showed a dose-response relationship, in which higher gradations of social disadvantage were associated with higher levels of risk.
Since these social disadvantages often overlap, the researchers looked at combinations as well and found them to be roughly additive in effect. Parental unemployment plus relative income poverty was associated with a 1.9 percent higher risk of offspring ADHD. Parental unemployment plus completion of no more than compulsory education was associated with a 3.2 percent higher risk. Parental relative income poverty plus completion of no more than compulsory education produced a 4.2 percent higher risk. Finally, Parental relative income poverty plus completion of no more than compulsory education plus unemployment was associated with a 4.9 percent higher risk.
The authors concluded, "This study shows that specific and well-measured parental social disadvantages in terms of unemployment, relative income poverty, and low educational attainment independently affect the risk of ADHD."
Maria Kellow, Chunsen Wu, Carsten Obel, "Cumulative social disadvantage and risk of attention deficit hyperactivity disorder: Results from a nationwide cohort study," SSM - Population Health (2020) 10, 100548, https://doi.org/10.1016/j.ssmph.2020.100548.
There has been consistent evidence of an association between ADHD and subjectively reported sleep problems even in patients not medicated for the disorder. There have also been studies using wrist-worn actigraphy (a wrist watch-like device that measures gross motor activity) and sleep lab-based polysomnography that measure objective sleep parameters.
What has been missing are large population-based cohort studies to explore the prevalence rates of different sleep disorders and medical prescriptions in ADHD.
Methods Used:
Sweden has a single-payer health insurance system and a series of national population registers that track virtually its entire population. Using the Swedish Total Population Register, a local research team created a cohort of all 6,470,658 persons born between 1945 and 2008. They linked this to the Swedish National Patient Register, which includes inpatient hospitalizations from 1975 to 2013, and outpatient specialist diagnoses from 2001 to 2013, to identify diagnoses of sleep disorders. They also linked to the Prescribed Drug Register, covering 2005 to 2013, to identify prescriptions for sleep medications.
Summary of Findings:
Overall, persons with ADHD were eight times more likely to be diagnosed with any sleep disorder relative to normally developing peers. Broken down by age, adolescents with ADHD were 16 times more likely to receive such diagnoses, young adults (18-30) twelve times more likely, children and mid-age adults (31-45) eight times more likely, and older adults six times more likely.
Broken down by specific sleep disorder diagnoses, relative to normally developing peers, persons with ADHD were:
As for sleep medication, relative to normally developing peers, persons with ADHD were:
Conclusion:
The team concluded, “Our findings also suggest that greater clinical attention should be directed towards addressing sleep problems in individuals with ADHD. This entails implementing proactive measures through sleep education programmes and providing both pharmacological and non-pharmacological approaches such as cognitive behavioural therapy and parental sleep training.”
Attention is a critical determinant of academic achievement, influencing domains such as language, literacy, and mathematics. To explore whether physical activity can improve attention in children with ADHD, an international team conducted a meta-analysis of peer-reviewed studies. The goal was to evaluate the impact of various physical activity regimens on attention-related outcomes in this population.
The researchers performed a comprehensive search of the medical literature to identify studies examining the effects of physical activity on attention in schoolchildren with ADHD. They included 10 studies with a total of 474 participants in their meta-analysis. The studies evaluated two main types of physical activity:
Additionally, they examined variations based on the frequency, duration, and type of control groups used in the studies. To assess consistency, they also analyzed heterogeneity (variability of outcomes) and checked for potential publication bias.
Key findings from the meta-analysis include:
The authors concluded that mentally engaging exercise is more effective than aerobic exercise in improving attention problems in schoolchildren with ADHD. Furthermore, higher frequency and longer duration of physical activity do not necessarily yield better outcomes.
This research underscores the importance of tailoring physical activity interventions to emphasize cognitive engagement over intensity or duration. By refining strategies, educators and parents can better support children with ADHD in achieving academic success. But take note: given the results from controlled studies, it seems clear that if there is a positive effect of exercise, it is very small so should not replace standard treatments for ADHD.
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Previous studies have examined how stimulant medications affect the brain in controlled settings, but less is known about their impact in real-world conditions, where children may not always take their medication consistently or may combine it with other treatments. A new study leverages data from the Adolescent Brain Cognitive Development (ABCD) study to explore how real-world stimulant use impacts brain connectivity and ADHD symptoms over two years.
Changes in Brain Connectivity Researchers used brain imaging data from the ABCD study to examine the functional connectivity—communication between brain areas—of six regions within the striatum, a brain area involved in motivation and movement control. They focused on how stimulant use influenced connectivity between the striatum and other networks involved in executive functioning and visual-motor control.
The study found that stimulant exposure was linked to reduced connectivity between key striatal areas (such as the caudate and putamen) and large brain networks, including the frontoparietal and visual networks. These changes were more pronounced in children taking stimulants compared to those who were not medicated, as well as compared to typically developing children. Importantly, this reduction in connectivity seemed to regulate certain brain networks that are typically altered in children with ADHD.
Symptom Improvement In addition to brain changes, 14% of children taking stimulants experienced a significant reduction in ADHD symptoms over the two-year period. These children showed the strongest connectivity reductions between the right putamen and the visual network, suggesting that stimulant-induced connectivity changes may contribute to improvements in visual attentional control, which is a common challenge for children with ADHD.
Why This Matters This study is one of the first to examine how stimulant use in real-world conditions affects brain networks in children with ADHD over time. The findings suggest that stimulants may help normalize certain connectivity patterns associated with ADHD, particularly in networks related to attention and control. These insights could help clinicians better understand the potential long-term effects of stimulant treatment and guide personalized approaches to ADHD management.
Conclusion Stimulant medications appear to alter striatal-cortical connectivity in children with ADHD, with some changes linked to symptom improvement. This research highlights the potential for stimulant medications to impact brain networks in ways that support attention and control, highlighting the importance of understanding how real-world medication use influences ADHD treatment outcomes.
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