Teens who drink more than five cans of non-diet, fizzy soft drinks every week are significantly more likely to behave aggressively, suggests research published online in the journal "Injury Prevention." This includes carrying a weapon and perpetrating violence against peers and siblings.

U.S. lawyers have successfully argued in the past that a defendant accused of murder had diminished capacity as a result of switching to a junk food diet, a legal precedent that subsequently became famous as the “Twinkie Defense.”

The researchers base their findings on 1,878 teens from 22 public schools in Boston.

The teens were asked how many carbonated non-diet soft drinks they had drunk over the past seven days.

The responses were divided into two groups: those drinking up to four cans over the preceding week (low consumption); and those drinking five or more (high consumption). Just under one in three respondents fell into the high consumption category.

The researchers then looked at potential links to violent behavior in this group, by asking if they had been violent towards their peers, a sibling, or a partner, and if they had carried a gun or knife over the past year.

Those who drank five or more cans of soft drinks every week were significantly more likely to have drunk alcohol and smoked at least once in the previous month.

But even after controlling for these and other factors, heavy use of carbonated non-diet soft drinks was significantly associated with carrying a gun or knife, and violence towards peers, family members and partners.

Just over 23 percent of those drinking one or no cans of soft drink a week carried a gun/knife, rising to just under 43 percent among those drinking 14 or more cans. The proportions of those perpetrating violence towards a partner rose from 15 percent in those drinking one or no cans a week to just short of 27 percent among those drinking 14 or more.

In all, for those teens who were heavy consumers of non-diet carbonated soft drinks, the probability of aggressive behavior was 9 to 15 percentage points higher - the same magnitude as the impact of alcohol or tobacco - the findings showed. “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,” conclude the authors of the study.