November 2, 2023
While influenza normally only threatens the elderly or those with complicating conditions, the 2009 H1N1 variant struck children particularly hard.
ADHD is known to be associated with inflammatory and immune-related disorders such as asthma, eczema, and allergic rhinitis. These disorders can aggravate respiratory infections such as influenza. Moreover, the cognitive deficits characteristic of ADHD - difficulty following instructions, reduced ability to control impulsive behavior and resulting nail-biting, and poor hand hygiene - can increase the probability of infection in the first place.
A Taiwanese research team explored how drug treatment for ADHD might affect the risk of childhood influenza. Only two drugs are approved in Taiwan for treating ADHD: the stimulant methylphenidate (MPH) and the non-stimulant atomoxetine. Because the latter is only recommended for patients who have unsatisfactory outcomes with MPH, MPH is the drug used in the vast majority of cases.
Taiwan is one of the relatively few countries that track the health care of its entire population in a comprehensive database, thanks to a single-payer health care system launched in1995. From the National Health Insurance Research Database, the Bureau of National Health Insurance in 2005 used random sampling to create a million-person Longitudinal Health Insurance Database (roughly five percent of the population).
From this latter database, the research team identified 9,826 patients newly diagnosed with ADHD. They excluded 1,786 with influenza before their ADHD diagnosis. After further excluding those outside the youth age brackets or who had gotten a flu shot during the year preceding enrollment, they were left with 5,259 patients with ADHD under age 18. Of these, 661 got influenza following diagnosis of ADHD.
In this ADHD cohort, 43 percent had not used any medication. Of the 57% who used medication, 20 percent did so for 90 days or less, and 37 percent for over 90 days.
After controlling for gender, age, level of urbanization, psychiatric or physical illnesses, and other medication use(sedative/hypnotics/anxiolytics), those prescribed MPH over 90 days were 38 percent less likely to get influenza requiring interaction with the health care system. There was a lesser reduction for those taking MPH 90 days or less, but it was not statistically significant.
A significant limitation is the fact that data from in-school vaccination programs are not included in the database used. If children receiving less or no medication were also less likely to be vaccinated, this unexplored covariate could explain the results. Further study is needed.
Hsuan Lee, VincentChin-Hung Chen, Yao-Hsu Yang , Ting-Yu Kuo, Tzu-Chin Lin, Shu-I Wu, Kai-LiangKao, Jun-Cheng Weng, Brent Allan Kelsen, Sophie Hsin-Yi Liang, "Decreased Risk of Influenza in Child and Adolescent Patients with Attention-Deficit Hyperactivity DisorderFollowing Methylphenidate Treatment: A Nationwide Cohort Study in Taiwan," NeuropsychiatricDisease and Treatment (2020), 16: 1309-1319, https://doi.org/10.2147/NDT.S242519.