In a study published in the British journal Injury Prevention, scientists reported that regular soda consumption increases the probability of a teenager engaging in an aggressive act by nine to 15 percent.
Adolescents who drank more than five cans of soft drinks per week (nearly 30 percent of the sample) were significantly more likely to have carried a weapon and to have been violent with peers, family members and dates, researchers wrote.
The Harvard researchers controlled outside factors such as race, gender, age, alcohol tobacco use, family life and sleep patterns, and were still confident in their conclusions. The study questioned about 1,900 public school students in metropolitan Boston area -- where crime is higher than in the suburbs.
What we found was that there was a strong relationship between how many soft drinks that these inner-city kids consumed and how violent they were, not only in violence against peers but also violence in dating relationships, against siblings, David Hemenway, a professor at the Harvard School of Public Health, told AFP.
It was shocking to us when we saw how clear the relationship was, he added.
What the researchers found is called a dose-effect, meaning that the more soda the students drank, the higher their inclination to violence. At one can of soda or less consumed a week, 23 percent of the teens carried a gun or a knife, 15 percent perpetrated violence toward a partner, and 35 percent had been violent toward peers.
On the other end, of the students who averaged 14 or more cans of soda per week, 43 percent carried a gun or a knife, 27 percent had been violent toward a partner, and nearly 60 percent had been violent toward peers.
There may be a direct cause-and-effect relationship, perhaps due to the sugar or caffeine content of soft drinks, or there may be other factors, unaccounted for in our analyses, that cause both high soft drink consumption and aggression, researches said.
We don't know why [there is this strong association], Hemenway told AFP. There may be some causal effect but it's also certainly plausible that this is just a marker for other problems - that kids who are violent for whatever reason, they tend to smoke more, they tend to drink more alcohol and they tend to maybe drink more soft drinks. We just don't know.
We want to look at it more carefully in following studies.