This review pooled 42 studies covering 728,136 people. Of these, 48,161 had ADHD (46,115 children and 2,046 adults). The comparison group held 679,975 people without ADHD (616,228 children and 63,747 adults).
People with ADHD were somewhat more likely to have obesity than people without it. The link was unlikely to be down to chance. It held in both children and adults, and it looked stronger in adults. It also held when the studies' adjusted results were pooled. ADHD was also linked with being overweight, based on 22 studies, though this link was weaker.
Among adults with ADHD, 28.2% had obesity. Among adults without ADHD, the share was 16.4%. Among children with ADHD, the share was 10.3%. Among children without ADHD, it was 7.4%.
A subset of 12 studies reported on people with ADHD who did and did not take medication. In those studies, the link with obesity showed up only in people who were not medicated. People taking medication were at no higher risk than controls.
The authors note several limits. Most data came from a single point in time, so the study cannot show that ADHD causes obesity. Studies defined obesity in children in different ways. Including unpublished data and leaving out weight-loss surgery samples may have added bias. The studies still disagreed with each other in most subgroup analyses. The medication finding rests on 12 correlational studies and cannot show that treatment lowers obesity risk.
The numbers Stats and what the terms mean
The statistics behind the plain-language claims above.
- Cortese, 2015: odds of obesity with ADHD versus controls, all 41 studies with unadjusted data, odds ratio=1.30, 95% CI=1.16-1.46.
- Cortese, 2015: odds of obesity in children and adolescents with ADHD, odds ratio=1.20 (95% CI=1.05-1.37).
- Cortese, 2015: odds of obesity in adults with ADHD, odds ratio=1.55 (95% CI=1.32-1.81).
- Cortese, 2015: odds of obesity using adjusted results, odds ratio=1.27 (95% CI=1.11-1.44).
- Cortese, 2015: share of adults with ADHD who had obesity, 28.2% (95% CI=22.8-34.4), versus adults without ADHD, 16.4% (95% CI=13.4-19.9).
- Cortese, 2015: share of children with ADHD who had obesity, 10.3% (95% CI=7.9-13.3), versus children without ADHD, 7.4% (95% CI=5.4-10.1).
- Cortese, 2015: odds of overweight with ADHD across 22 studies, odds ratio=1.17 (95% CI=1.01-1.36).
- Cortese, 2015: odds of obesity in unmedicated people with ADHD, odds ratio=1.43, 95% CI=1.23-1.67.
- Cortese, 2015: odds of obesity in medicated people with ADHD, odds ratio=1.00, 95% CI=0.87-1.15. What the terms mean:
- Odds ratio compares how likely something is in one group versus another, where 1.00 means no difference and higher numbers mean greater odds.
- 95% CI is the range the true value most likely falls in, and a range that includes 1.00 means the difference could be down to chance.
Source: Samuele Cortese, Carlos Renato Moreira Maia, Diane St. Fleur, et al.. Association Between ADHD and Obesity: A Systematic Review and Meta-Analysis. American Journal of Psychiatry (2015). doi:10.1176/appi.ajp.2015.15020266