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CASE VIGNETTE
“Kate” is a 17-year-old Caucasian female with a history of attention-deficit/hyperactivity disorder (ADHD), diagnosed at age 10 years. She presented with primarily inattentive symptoms and minimal issues with hyperactivity or impulsivity. She has a history of myopia and has worn eyeglasses since age 13 years. She was also diagnosed with asthma at age 6 years. Her body mass index is in the 40th percentile.
Kate had a positive response to treatment with methylphenidate, which she continues to take, although she is still sometimes easily distracted. At an outpatient visit, her mother asks whether Kate’s asthma could impact on her ADHD symptoms. As Kate’s psychiatrist, how would you respond?
Increasing evidence suggests that ADHD is associated with physical comorbidities, including asthma and obesity.1 A recent birth cohort study found cross-sectional associations between ADHD symptoms, asthma, and sleep problems in early and middle childhood and adolescence.2
There may be a bidirectional association between ADHD and physical conditions, as well as common underlying risk factors.3 Few studies have investigated longitudinal associations between ADHD and physical conditions.
The Current Study
Reed and colleagues4 used a large-scale population-representative sample to investigate the hypothesis that the cumulative number of physical health conditions across childhood are associated with ADHD symptoms in adolescence (age 17 years), controlling for cumulative environmental risk, ADHD medications, and ADHD symptoms at age 3 years.
The authors used data from the Millennium Cohort Study, which contains longitudinal data on > 19,000 UK families with children born between 2000 and 2002. Data have been collected in 7 waves, at ages 9 months and 3, 5, 7, 11, 14, and 17 years. Only the first sibling in each family was included. Participants were also excluded if data on the biological mother was unavailable, if physical health predictor variables were missing, or if outcome data at age 17 years was missing. The present study included 8059 participants.
The parent-reported hyperactivity/inattention subscale of the Strengths and Difficulties Questionnaire (SDQ), which predicts ADHD diagnosis,5 was collected at age 17 years, and SDQ score at age 3 years was also included as a potential confounding factor. Approximately 174 children in the cohort were diagnosed with ADHD by age 17 years. Parents were asked about their child’s physical health at each wave, including diagnoses and hospitalizations. Physical conditions were grouped into 4 clusters:
- Sensory (eyesight, hearing)
- Atopic (eczema, asthma, hay fever)
- Neurological (epilepsy, sleep problems, movement problems, stutter)
- Cardiometabolic (obesity, diabetes, heart problems)
Risk factors were grouped into 5 cumulative risk indices:
- Prenatal
- Perinatal
- Postnatal environment
- Postnatal maternal well-being
- Socioeconomic status and demographics
At age 14 years, data on ADHD medications were also obtained. Data were analyzed using stepwise multiple linear regression to analyze the relationship between physical health clusters and ADHD symptoms at age 17 years, controlling for environmental risk indices, ADHD medications, and SDQ score at age 3 years. Binary logistic regression models were also used with ADHD diagnosis as the outcome.
Approximately 91 children were taking ADHD medication, and the average SDQ score at age 17 years was 2.6. After adjusting for confounders, sensory and neurological clusters were significantly associated with ADHD symptoms as a continuous measure at age 17 years (β=0.06 for each), and the model explained 21% of the variance.
In binary logistic regression analyses, both the sensory cluster (OR=1.31, 95% CI 1.04-1.65) and the neurological cluster (OR=1.94, 95% CI 1.48-2.53) predicted ADHD diagnosis. The odds of an ADHD diagnosis approximately doubled with each additional neurological condition.
Study Conclusions
The investigators concluded that this was the first study to analyze the longitudinal association between physical conditions in childhood and ADHD symptoms. Sensory and neurological clusters, but not the atopic or cardiometabolic clusters, were significant predictors of hyperactivity/inattention symptoms at age 17 years. Participants with predating neurological issues were almost 2 times more likely to have an ADHD diagnosis at age 17 years.
Study strengths included the large cumulative sample size, the availability of longitudinal data, and consideration of potential confounding effects of environmental risk factors and ADHD medications. Limitations include that the SDQ is not designed as a screening instrument for ADHD, and only a small subset of participants had been clinically evaluated for ADHD.
The investigators did not explore ADHD symptoms as predictors of physical health (the reverse relationship). Data were not available to analyze the effect of parental history of ADHD on these associations.
The Bottom Line
Findings suggest possible biological commonalities between physical disorders in childhood and ADHD symptoms in adolescence. Clinicians should monitor for symptoms of hyperactivity and inattention in children with sensory and neurological disorders.
Dr Miller is a professor in the Department of Psychiatry and Health Behavior at Augusta University in Georgia. He is on the Editorial Board and serves as the schizophrenia section chief for Psychiatric Times®. The author reports that he receives research support from Augusta University, the National Institute of Mental Health, and the Stanley Medical Research Institute.
References
1. Arrondo G, Solmi M, Dragioti E, et al. Associations between mental and physical conditions in children and adolescents: an umbrella review. Neurosci Biobehav Rev. 2022;137:104662.
2. Galéra C, Cortese S, Orri M, et al. Medical conditions and attention-deficit/hyperactivity disorder symptoms from early childhood to adolescence. Mol Psychiatry. 2022;27(2):976-984.
3. Hanć T, Cortese S. Attention deficit/hyperactivity-disorder and obesity: a review and model of current hypotheses explaining their comorbidity. Neurosci Biobehav Rev. 2018;92:16-28.
4. Reed C, Cortese S, Larsson H, et al. Longitudinal associations between physical health conditions in childhood and attention-deficit/hyperactivity disorder symptoms at age 17 years [published online ahead of print, 2023 Jul 3]. J Am Acad Child Adolesc Psychiatry. 2023;S0890-8567(23)00372-6.
5. Hall CL, Guo B, Valentine AZ, et al. The validity of the Strengths and Difficulties Questionnaire (SDQ) for children with ADHD symptoms. PLoS One. 2019;14(6):e0218518.