What science tells us about casual impact of sugar on behavior problems

The following op-ed by FIU Associate Professor of Psychology Joseph Raiker was originally published in Psychology Today. Raiker’s research focuses on understanding neurocognitive dysfunction in individuals with attention-deficit/hyperactivity disorder and identifying optimal methods of integrating this knowledge into treatment outcome research.

Will Halloween Candy Cause My Child to Misbehave?

By Joseph Raiker

With Halloween just around the corner, kids delight in hearing various stories and ancient tales and wondering whether or not they are true. Additionally, it is likely that candy, cookies, and other sugary treats are going to be just an arms-length away, placing many parents on edge when considering what will happen if they let their child have just one more piece of candy.

This “Should I or shouldn’t I?” decision is often informed by one ancient tale that continues to persist—sugary treats cause children to misbehave! Belief that there is a relationship between sugary treats and behavior problems is often reflected in comments such as “Whoa! What did she have for lunch? She’s bouncing off the walls” or, after a sugar-laden birthday party spread, a parent might say something like “I’m not sure I’ll ever get him to go to sleep after all that sugar.” Fortunately, while we may never be able to separate fact from fiction when it comes to stories of goblins and ghouls, there have been numerous scientific studies examining whether sugar is associated with problematic behaviors in children.

One of the earliest experimental studies examining the impact of sugar on the behavior of children included 16 boys between the ages of 6 and 9 with a diagnosis of ADHD (formerly ADDH; Milich & Pelham, 1986). These boys were observed for two days during which they were given placebo and observed for two days during which they were given sugar in amounts adjusted for body weight. The order in which they received placebo or sugar was randomized. After being provided with sugar or placebo, the children participated in a variety of activities (e.g., sports, classroom assignments) during which their behavior was observed and recorded by trained observers who did not know whether the child had received sugar or placebo (i.e., blinded). This type of blinded design is critical as it reduces the chance that observers will draw faulty conclusions simply because they know that the child has received sugar or placebo. Across 25 five different variables including, but not limited to, following rules, interacting appropriately and positively with peers, staying on task during assignments, and completing math and reading assignments, no significant differences were found between the sugar condition and the placebo condition. Despite the study’s strengths, it is notable that it included a relatively small sample of children, all boys, and children with a diagnosis of ADDH (what we now call ADHD). With that said, however, it added to a growing list of other studies suggesting no causal role for sugar on problematic behaviors in children.

Fortunately, nearly a decade later, a meta-analysis examining whether sugar has a negative impact on behavior or cognition in children was conducted (Wolraich, Wilson, & White, 1995). Meta-analyses are unique in that, rather than relying upon data from a single study, they combine most or all studies related to a particular topic and provide a summary of our understanding of a topic given the available evidence. Given that no study is perfect, this type of approach can provide a more definitive conclusion regarding a scientific question such as “Does sugar make kids more likely to misbehave?” This particular meta-analysis identified all studies that were similar in design to the one described above. Notably, the meta-analysis was much more expansive in that it did not just include studies of children with ADHD but instead included studies on children regardless of their diagnosis. Additionally, the studies used different types of sugar (e.g., sucrose, glucose) and placebo (e.g., Saccharin, Aspartame) conditions, included females, as well as a variety of outcomes. The results of 16 studies across multiple outcomes including tests, aggression, observations of behavior, and teacher ratings were examined. Collectively, not a single significant negative outcome as a result of sugar was found dealing yet another blow to the prevailing notion that sugar results in negative effects on behaviors or cognition. Whether a child had a diagnosis of ADHD did not change the finding that sugar did not have a negative impact on any of these outcomes.

Despite this evidence, why does the notion that sugar causes children to misbehave persist? While it is difficult to know for sure, Milich and Pelham (1986) note that the persistence of this belief may reflect the settings in which children are likely to receive sugary snacks. For example, rarely does a teacher pass out cupcakes in the middle of a math test. Instead, cupcakes are often distributed during unstructured activities such as lunch or recess when kids may already be likely to exhibit greater behavior problems relative to structured activities. As a result, we may draw faulty conclusions that because our observations of children’s misbehavior and sugar intake are associated, they must be causally related to one another. The experimental studies described above, however, have failed to identify a causal association between the two. Unfortunately, the suspected causal role for sugar on problematic behaviors has resulted in the use of elimination diets for children with ADHD which, despite lacking sufficient scientific support, are sometimes recommended in lieu of other well-established evidence-based interventions such as behavioral treatment or stimulant medication.

It is important to note that while there is no substantive evidence that sugar is likely to result in behavior problems in children, ingestion of large quantities of sugar does have the potential to result in other maladaptive health outcomes (e.g., diabetes) and may be associated with other health problems. Further, in rare cases (approximately 8% of children; Centers for Disease Control and Prevention; Gupta et al., 2018), some children may have a food allergy which results in behavioral or mood changes that should be evaluated by a physician, allergist, or nutritionist if parents are concerned. Ultimately, while Halloween and the holiday season may bring a number of things for us to be frightened of, or worried about, in most cases, fear that an extra piece of candy or additional cookie is going to cause a child to misbehave does not appear to have any scientific support.


Milich, R., & Pelham, W. E. (1986). Effects of sugar ingestion on the classroom and playgroup behavior of attention deficit disordered boys. Journal of Consulting and Clinical Psychology, 54(5), 714.

Wolraich, M. L., Wilson, D. B., & White, J. W. (1995). The effect of sugar on behavior or cognition in children: a meta-analysis. JAMA, 274(20), 1617-1621.


Gupta, R. S., Warren, C. M., Smith, B. M., Blumenstock, J. A., Jiang, J., Davis, M. M., & Nadeau, K. C. (2018). The public health impact of parent-reported childhood food allergies in the United States. Pediatrics, 142(6).