Artificial colors or a sodium benzoate preservative (or both) equal to typical dietary intakes resulted in increased hyperactivity in 3-year-old and 8/9-year-old children in the general population (randomized double-blind, placebo-controlled trial).
Another randomized, placebo-controlled trial showed that food additives exacerbate hyperactivity in children with ADHD. These findings show that increased hyperactivity is not limited to children with ADHD but can also be seen in the general population and across the range of severities of hyperactivity.
There have also been a couple of studies shown that a diet that eliminates food additives can improve behavior in children with hyperactivity.
These studies do not go without limitations. For example, the effects on behavior were only significant when parents analyzed behavior and not a clinician. This could have to do with the timing of the intake of the food additives. The parents are with their children round the clock whereas a clinician is only seeing a child once or twice a week.