Maternal grandmothers who were underweight before becoming pregnant were more likely to have a grandchild diagnosed with ADHD than women in other BMI categories, a cohort study showed. “There is growing evidence from animal research that peripregnancy exposures can have effects that are passed on to more than just the next generation,” Marc Weisskopf, PhD, ScD, a professor of environmental epidemiology and physiology at the Harvard T.H. Chan School of Public Health, told Healio. “But this is very hard research to do in humans because of the need to collect data from, and follow, multiple generations.”