Attention-deficit/hyperactivity disorder (ADHD) might contribute to obesity by reducing physical activity – a relationship that can also be mediated by the features of the urban environment in which a person lives. That is the conclusion of a new study published this week in the open-access journal PLOS Complex Systems by Tian Gan, Rayan Succar, and Maurizio Porfiri of the Tandon School of Engineering at New York University, U.S., and Simone Macrì of the Italian National Institute of Health, Italy.
For years, scientists have suspected that impulsivity – including conditions like ADHD – may increase the risk of obesity, but much of the evidence has focused on individual traits and behaviors, placing limited attention towards environmental and social factors.
In the new study, researchers used data from 915 U.S. cities to explore how impulsivity and obesity vary with city size and urban conditions. They found that both obesity and ADHD are less common in larger cities. The team then analyzed how different cities vary from this pattern, accounting for their population sizes and features such as access to mental health care, education, and food security.
Their results suggest that ADHD increases obesity indirectly by reducing physical activity, and this relationship is influenced by urban lifestyle factors. The researchers discovered that in cities with fewer opportunities for physical activity or more food insecurity, the link between ADHD and obesity was stronger. In contrast, cities with better access to mental health care and higher education levels seemed to weaken that link. To test whether these city-level findings hold true for individuals, the researchers also analyzed health data from over 19,000 children. They confirmed that kids with more severe ADHD symptoms were less physically active and more likely to be obese — supporting the idea that impulsivity contributes to obesity, and that this link can be shaped by factors like physical activity, food access, and household education.
"These findings underscore the importance of city-level interventions in mitigating the impact of impulsivity disorders on the obesity epidemic," Dr. Maurizio Porfiri says.
Ph.D. student Tian Gan adds: "Our research reveals a surprising urban advantage: as cities grow, both obesity and ADHD rates decrease proportionally. Meanwhile, mental health services become more accessible, helping combat physical inactivity—a key link between ADHD and obesity. This pattern suggests larger cities offer protective factors against these interconnected health challenges."
