ADHD Linked to Several Physical Health Conditions

Ebba Du Rietz, PhD

New research shows attention deficit/hyperactivity disorder (ADHD) is linked to several different physical health conditions that could remain prevalent throughout life.

A team, led by Ebba Du Rietz, PhD, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, investigated the phenotypic and aetiological associations between ADHD and different physical health conditions across adulthood.

Background

ADHD might increase the risk of several other physical health conditions. However, there are very few conditions that have been thoroughly studied in relationship with ADHD and little research on this link in older ADHD patients.

In the register study based in Sweden, the researchers identified full-sibling and maternal half-sibling pairs born between 1932-1995 using the Population and Multi-Generation Registers.

The team included full-siblings who were not twins and did not have half-siblings andexcluded those who died or emigrated prior to 2005.

Cohort

A total of 4.7 million individuals were identified, who formed 4.3 million unique sibling pairs and 1.8 million family clusters. The mean age of the patient population was 47 years old.

In the analysis, they obtained ICD diagnoses form the National Patient Register for physical conditions when each participant was at least 18 years old from inpatient and outpatient services.

The investigators estimated the associations between ADHD and 35 different physical conditions in individuals and across sibling pairs using logistic regression models and estimated the extent of genetic and environmental factors accounting for this association using quantitative genetic modelling.

The Link

Adults with ADHD had increased risk for 34 of the 35 physical conditions, compared to individuals without ADHD. The strongest association was with nervous system disorders including sleep disorder, epilepsy, and dementia (OR, 1.50-4.62) and respiratory diseases, such as asthma and chronic obstructive pulmonary diseases (OR, 2.42.-3.24).

A sex-stratified analysis showed similar patterns between male and female participants.

However, there was a stronger cross-disorder association found between full-siblings than between half-siblings for nervous system, respiratory, musculoskeletal, and metabolic diseases (P <0.007).

Quantitative genetic modeling showed the associations were generally explained by shared genefactors (60-69% of correlations), except for associations with nervous system disorders, which were largely explained by non-shared environmental factors.

“This mapping of aetiological sources of cross-disorder overlap can guide future research aiming to identify specific mechanisms contributing to risk of physical conditions in people with ADHD, which could ultimately inform preventive and lifestyle intervention efforts,” the authors wrote. “Our findings highlight the importance of assessing the presence of physical conditions in patients with ADHD.”

Sleep

Earlier this year, researchers identified a better understanding as to why patients with ADHD suffer from greater rates of sleep issues, including insomnia and excessive sleepiness.

Impaired sleep is a known risk factor for several negative health outcomes, such as deficits in executive function, attention, and impulse control, which all happen to be symptoms of ADHD. About half of ADHD patients report sleep disturbances, with delayed sleep onset being the most commonly reported symptom.

Sleep deprivation is also linked to reduced dorsolateral prefrontal activity, as well as difficulty regulating attentional resources. This could help explain the inability to attend to a stimulus in the presence of distractions or engage in goal-directed behavior.

The study, “Mapping phenotypic and aetiological associations between ADHD and physical conditions in adulthood in Sweden: a genetically informed register study,” was published online in The Lancet Psychiatry.