We already know that sugary soft drinks aren't exactly great for your health, contributing to obesity, diabetes, and other health problems. And now there's this: A new study in the journal Pediatrics says drinking too much soda can make children more likely to get into fights and break their friends' toys.

Researchers from the public health schools at Columbia and Harvard followed the habits of about 3,000 moms and their 5-year-olds in 20 large cities. They found that 43 percent of the kids consumed at least one soft drink per day, and that those who swilled four sodas or more daily were more than twice as likely to show signs of attention problems and aggression, such as destroying others' belongings or physically attacking people.

Even after adjusting for sociodemographic factors — such as maternal depression, intimate partner violence, and paternal incarceration — soft drink consumption was still associated with aggression, withdrawal, and attention problems.

"With every increase in soda consumption, we saw an increase in behavior problems," says Shakira Suglia, a study author and associate professor of epidemiology at Columbia University.

The study's conclusions confirmed suspicions of some experts who deal with preschoolers. "It makes sense on a lot of levels," Ben Belnap, a Utah child psychologist, tells The Salt Lake Tribune. "It sort of seems like a no-brainer."

Why would soda make kids misbehave? The researchers couldn't say, precisely, but they suggested that any of a number of ingredients — including high-fructose corn syrup and caffeine — might be enough to make a child unruly. Alexandra Sifferlin at TIME argues that caffeine is the most likely culprit.

Other studies connected the compound with changes in hormone levels that could alter the way still developing brains perceive and evaluate risk... The sugar in sodas may also affect behavior, though that connection is murkier. [TIME]

But some people suggest another factor should be added to the list of culprits: Slack parenting. "What kid is drinking four sodas a day?" asks Eve Vawter at Mommyish. "I'm a terrible Diet Coke addict. Yes, I know how utterly bad it is for me and yes, I will quit the Satan juice, and yes, I know, I know. But even though I feel like I consume a large amount of the DC daily, even I don’t drink FOUR a day and I'm a grownup person!"