October 16, 2021
What are the links between ADHD and physical ailments in adults? And, where such links exist, how can we tease out where they are due to genetics, shared environment, or unshared environmental influences?
An international research team used the Swedish population and health registers to explore these links in an entire national population. They were able to do this because Sweden has a single-payer national health insurance system, cross-referenced with the population and other national registries through personal identification numbers.
This study identified full-sibling and maternal half-sibling pairs born from 1932 through 1995, through the Population and Multi-Generation Registers. This yielded a total of 4,789,799 individuals - consisting of 3,819,207 full-sibling pairs and 469,244 maternal half-sibling pairs, and 1,841,303family clusters (siblings, parents, cousins, spouses). Roughly half were men, the other half women.
After adjusting for sex and birth year, those with ADHD were at significantly higher risk of a wide range of physical ailments, when compared with individuals without ADHD:
· Over four times as likely to have sleep disorders or develop alcohol-related liver disease;
· Roughly three times as likely to develop the chronic obstructive pulmonary disease, epilepsy, and fatty liver disease;
· Over two and a half times more likely to become obese.
Overall, ADHD was significantly associated with 34 of the 35 physical diseases studied, rheumatoid arthritis being the only exception.
Comparing men with women, women with ADHD were at significantly greater risk of atrial fibrillation, urolithiasis, sleep disorders, and asthma than men with ADHD. Conversely, men with ADHD faced a greater risk of thyroid disorder than women with ADHD.
Between-sibling analyses showed that full siblings of individuals with ADHD were at significantly increased risk for 27 of the 35 physical ailments, suggesting that shared familial factors contributed to the co-occurrence of the conditions. This remained true even after adjusting for the occurrence of ADHD in full siblings.
These associations were generally reduced in maternal half-siblings of individuals with ADHD. The associations between full-siblings were significantly stronger than between maternal half-siblings for type 1 diabetes, obesity, kidney infections, back or spine pain, migraine, sleep disorders, asthma, and chronic obstructive pulmonary disease.
Keep in mind that full-siblings on average share half of their genes, whereas maternal half-siblings share only a quarter of their genes. Maternal (as opposed to paternal) half-siblings were chosen as a basis for comparison because they are typically brought up together in the same family setting, and thus are similar to full-siblings in having a shared family environment. Reduced risk in maternal half-siblings would therefore signal a genetic component to the risk.
Given that ADHD is itself a nervous system disorder, it is unsurprising that it correlated most strongly with other nervous system disorders, with a medium effect size (r=.23). Genetic factors explained over a quarter of the correlation, shared environmental factors over a seventh, and non-shared environmental factors the other three-fifths. The latter could point to environmental risk factors that influence both ADHD and nervous system diseases.
Small-to-medium correlations were found with metabolic, respiratory, and musculoskeletal disease groups, with genetic factors explaining roughly two-thirds of the correlation, and non-shared environmental factors most of the rest.
The authors concluded that "adults with ADHD are at increased risk of a range of physical conditions, across circulatory, metabolic, gastrointestinal, genitourinary, musculoskeletal, nervous system, respiratory, and skin diseases. Most physical conditions showed familial associations with ADHD (mainly from genetic factors). Our findings highlight the need for rigorous medical assessment and care in adult patients with ADHD, and suggest long-term consequences of age-related diseases."
Ebba Du Rietz, Isabell Brickell, AgnieszkaButwicka, Marica Leone, Zheng Chang, Samuele Cortese, Brian M D'Onofrio, Catharina A Hartman, Paul Lichtenstein, Stephen V Faraone, Ralf Kuja-Halkola, Henrik Larsson, "Mapping phenotypic and aetiological associations between ADHD and physical conditions in adulthood in Sweden: a genetically informed register study," Lancet Psychiatry (2021), vol. 8, issue 9, 774-783, published online, https://doi.org/10.1016/S2215-0366(21)00171-1.
According to Fosco et al. (2019), “Inhibitory control has long been considered a central neurocognitive process in ADHD, with ADHD groups typically showing medium-sized impairments relative to their typically-developing peers on common inhibition paradigms.”
Learning to play a musical instrument requires effective coordination of physical movements and sound signals to produce music. Musical training involves repetitive practice, perfecting connections between perceptions, muscular actions, and cognition.
Noting that listening to music activates the brain’s reward circuits in both children and adults, that “Being internally motivated during learning experiences increases learning capacity and efficiency, and this greater engagement is reflected in increased electrical brain activity following musical training,” and that “Training music in a social environment increases positive feelings of bonding through shared emotions and group synchrony,” a Montreal-based research team carried out a systematic review and meta-analysis of the peer-reviewed medical literature from 1980 to 2023 to learn what effect music training might have on inhibition control.
Outcomes:
The team found eight randomized controlled trials (RCTs) and 14 other longitudinal studies that met search criteria, including:
Meta-analysis of all 22 longitudinal studies with a combined total of 1,734 participants yielded a small-to-medium effect size improvement in inhibitory control. Variation (heterogeneity) in outcomes between individual studies was small, and there was no sign of publication bias. Restricting the analysis to the eight RCTs with a combined total of 641 participants, however, yielded a medium-to-large effect size improvement, with negligible heterogeneity, meaning the outcome was consistent across RCTs.
The Take-Away: The team concluded, “Music training plays a privileged role compared to other activities (sports, visual arts, drama) in improving children’s executive functioning, with a particular effect on inhibition control.” I cannot, however, recommend this as a therapy for ADHD until RCTs show it reduces symptoms of ADHD and/or real world impairments associated with the disorder.
Organic farming aims to protect biodiversity, promote animal welfare, and avoid using pesticides and fertilizers made from petrochemicals. Some pesticides are designed to target insects’ nervous systems but can also affect brain development and health in larger animals, including humans.
Many people believe organic food is healthier than conventionally produced food, which might be true for certain foods and health factors. But does eating organic food during pregnancy impact the chances of a child developing ADHD or autism spectrum disorder (ASD)?
In Norway, researchers can use detailed national health records to study these connections on a population-wide level, thanks to the country’s single-payer healthcare system and national registries.
The Norwegian Mother, Father, and Child Cohort Study (MoBa) invites parents to participate voluntarily and has a 41% participation rate. The study includes:
For this research, a team tracked 40,707 mother-child pairs from children born between 2002 and 2009. They used questionnaires to measure how much organic food mothers consumed during pregnancy. ADHD and ASD symptoms in children were assessed using validated rating scales.
The final analysis included:
The researchers adjusted for factors like maternal age, education, previous pregnancies, BMI before pregnancy, smoking and alcohol use during pregnancy, birth year and season, and the child’s sex.
The researchers concluded that eating organic food during pregnancy has no meaningful effect on the likelihood of a child developing ADHD or ASD. They stated, “The results do not indicate any clinically significant protective or harmful effects of eating organic food during pregnancy on symptoms of ADHD and ASD in the offspring. Based on these findings, we do not recommend any specific advice regarding intake of organic food during pregnancy.”
Infertility affects about one in six couples worldwide. To address this, medical experts have developed Assisted Reproductive Technologies (ART), including In Vitro Fertilization (IVF) with or without Intra-Cytoplasmic Sperm Injection (ICSI).
Some research suggests that children conceived through ART might have higher rates of intellectual disabilities, cerebral palsy, cancer, and neurological issues compared to children conceived naturally. However, studies looking at a possible link between ART and ADHD have produced mixed and conflicting results.
Until now, there hasn’t been a meta-analysis examining the connection between ART and ADHD. A South Korean research team has conducted the first systematic review and meta-analysis on this topic. Their final analysis included eight studies with a total of over ten million participants, comprising six cohort studies and two cross-sectional studies.
The research focused on two types of studies:
Both types of studies are observational, meaning they don’t involve controlled experiments and can be influenced by confounding factors. So they can document interesting associations, not causality. The studie were mostly large-scale national studies and used clinical ADHD diagnoses.
The researchers concluded that while there may be a small association between ART and ADHD, the effect is minimal, and the results are influenced by differences in study designs. They advised interpreting these findings with caution, noting, “The limited effect size and inherent heterogeneity underscore the need for cautious interpretation.”
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