Middle-school students who consume energy drinks could have more trouble in school than those who do not.

Researchers found kids who consume these heavily sweetened drinks are 66 percent more likely to show signs of hyperactivity and inattention, Yale University reported. The study's authors recommend that children should avoid these types of drinks altogether.

The researchers surveyed 1,649 middle-school students from Connecticut and found boys were more likely to consume these drinks than girls. They also observed that black and Hispanic boys of this age were more likely to consume the drinks than white students.

"As the total number of sugar-sweetened beverages increased, so too did risk for hyperactivity and inattention symptoms among our middle-school students. Importantly, it appears that energy drinks are driving this association," said professor Jeannette Ickovics, director of CARE (Community Alliance for Research and Engagement) at the School of Public Health. "Our results support the American Academy of Pediatrics recommendation that parents should limit consumption of sweetened beverages and that children should not consume any energy drinks." 

More research is needed to fully understand the impact of the drinks on children, but the findings suggest a key link between the drinks and school performance. These drinks contain as much as 40 grams of sugar each, and the students in the study consumed an average of two drinks per day with a range of zero to seven daily drinks. Health experts recommend children consume no more than 21 to 33 grams of sugar per day depending on their age.

In addition to their influence on hyperactivity and concentration, these drinks can also play a significant role in childhood obesity. In the U.S., sugar-sweetened beverages are the number one contributor of daily calories for obese children.

The study was co-authored by other researchers from CARE, the Rudd Center for Food Policy and Obesity, and the New Haven Public Schools.