Childhood Development: ADHD and Problem Behavior

Two new studies were recently published that shed light on several aspects of childhood behavioral development. The first has to do with how the brains of children with Attention Deficit / Hyperactivity Disorder (ADHD) develop differently from those of normal children. The second study, entitled "School Readiness and Later Achievement," assessed the power of early childhood social and academic skills to predict later math and reading achievement. I choose to discuss both of these studies because they are related in that they both examine aspects of childhood behavior that is often deemed unacceptable and in need of treatment. In the former case of ADHD, this treatment is often pharmaceutical. I learned about this new research from an article in the New York Times entitled “Bad Behavior Does Not Doom Pupils, Studies Say.” Although I think this headline might be a little too optimistic, both studies should be at least slightly encouraging to parents.

The ADHD brain development study involved 446 children, half of whom had been diagnosed with ADHD. Each of the children’s brains was scanned using MRI two or more times at about three year intervals between their early preschool years and young adulthood. The researchers examined the images of the brains to ascertain the thickness of over 40,000 cortex sites. Childhood brain development follows a pattern first of cortex thickening and later thinning when unused neurons are pruned away. They found that half of the cortex sites gained peak thickness about three years later, at about 10.5 years of age in the group with ADHD versus 7.5 in the control group (see picture on left). Nevertheless, the brains of children in both groups followed the same general developmental pattern. The brain’s frontal cortex was one of the areas where the children with ADHD showed the most delay in development. This area is thought to be responsible for many behaviors that are disturbed in people with ADHD, such as controlling impulses, focusing attention, and organizing complex tasks. Notably, one area of the brain, the motor cortex, actually matured faster in the children with ADHD which may explain the fidgetiness and excessive movement that sometimes characterize the hyperactive form of the disorder.

The second study set out to analyze which characteristics of preschool children would best predict their “later teacher ratings and test scores of reading and math achievement.” Among the early traits of preschool students, they found that school-entry math skills best predicted later reading and math performance, followed by early language and reading skills, and then attention skills. The most surprising result of the study was that there was no correlation between early “problem behaviors and social skills” and later math and reading achievement (see image at right). According to the New York Times article, “educators and psychologists have long feared that children entering school with behavior problems were doomed to fall behind in the upper grades.” Fundamentally, what the study says is that children who enter school being good at math and reading tend to continue to be good at math and reading regardless of whether or not they have poor social skills or act out. Put this way, the result does not seem as surprising. However, the researchers did attempt to control for the preschoolers’ cognitive ability, although they admitted that “despite our ability to control for cognitive ability … and despite our controls for concurrent reading skills in all six studies, it remains possible that our surprisingly large school-entry math coefficients overstate causal impacts.” Simply stated, the correlation between early math performance and later math and reading performance may just be the result of smart children being more likely to have early math skills than their less intellectually gifted peers. Nonetheless, just because early behavior and social skills don’t correlate with later academic achievement doesn’t mean nothing should be done to correct problem behavior, as being able to do math is of little use if a person is unable to interact with others.

Both of these studies should at the very least offer comfort to parents that are worried that any psychological or behavior problems their young children may have now will have a detrimental effect on their children’s lives forever. The ADHD brain imaging study shows that the brains of children who are diagnosed with ADHD at a young age develop in essentially the same pattern as those of normal children just a little bit later. Although it’s too early to tell, perhaps this new information will ease the pressure on parents to medicate their young children for ADHD if in many cases the disorder will go away on its own with a little patience. ADHD such as methylphenidate and amphetamine can help in some cases, but they have also been known to have serious side effects such as appetite suppression which in turn may cause stunted growth in young children. As for the second study, while it is very limited in scope, it may reassure some parents dealing with unruly children that the unruly behavior is at least an isolated problem and most likely will not affect academic performance.

Food Additives: Are they causing hyperactivity in children?

A recent study suggests there may be a link between common food additives and hyperactive behavior in children. The idea that food additives cause hyperactivity is not new. Dr. Ben F. Feingold first introduced a diet free of food additives as a cure for attention-deficit/hyperactivity disorder (ADHD) in the 1970s. However his method never gained widespread support in the medical community and was heavily criticized by food companies involved in making or distributing food additives. The new research, financed by Britain’s Food Standards Agency and published in The Lancet, is the first double-blind placebo-controlled study of the effect of food additives on behavior.

The three-week study of over 300 children involved two different age groups: 3-year olds and 8 and 9-year olds. Each child spent one week drinking one of three fruit drinks: one containing the amount of additives found in a typical British child’s diet, another without any additives, and the last containing a lower concentration of additives than the first. All three drinks were designed to taste the same. Researchers, ignorant of which children had received which drink, then observed the behavior of the children, paying close attention to the children’s’ attention spans, fidgetiness, restlessness, hyperactivity and other behaviors associated with ADHD. The study found that children were significantly more likely to display these ADHD-like behaviors when drinking the drinks with higher levels of additives. The effect was more pronounced in the 3-year olds than the 8 and 9-year olds. In addition, there were strong individual differences between the children, meaning some did not respond at all to the additives and others responded strongly.

One limitation of the study is that the additive-containing drinks contained a variety of different additives, making it impossible to determine specifically what compound is linked to the behavioral changes. The additive-containing drinks contained a variety of artificial food colorings as well as the compound pictured on the left, sodium benzoate, a common preservative. Sodium benzoate, however, is not only found artificially in foods as a preservative. It is also found naturally in cranberries and prunes.


One obvious question the results of the study bring up is whether these kinds of food additives are causing the high number of ADHD diagnoses in the United States. No other country diagnoses the disorder in children at anywhere near the rate that we do. In addition, the United States consumes 90% of the world’s methylphenidate, a common drug used to treat ADHD, also known by the brand name Ritalin. Some psychologists have questioned whether or not the high rate of diagnoses in the United States has more to do with cultural pressure on children to perform well in school rather than a real mental disorder. The results of the food-additive study, however, suggest that there may be other non-cultural reasons for the high rates of ADHD seen in the United States. Perhaps American children consume more food additives than children in other countries. Given the sheer number of colored and processed foods seen on a regular trip to an American grocery store, this is not hard to imagine. It would be interesting to see a study on the rate of food additive consumption compared to ADHD diagnosis across different countries.

Although it is easy and interesting to speculate on whether additives cause hyperactivity and ADHD in children, it is too early to jump to these kinds of conclusions. As mentioned earlier, there was a high degree of individual difference between children in the study with some children being much more sensitive to the presence of additives than others. It may be the case that the more sensitive children are already more hyperactive or predisposed to ADHD-like symptoms and the additives just exacerbate the problem rather than additives causing ADHD to appear in children who otherwise would be completely normal.

Some scientists in the United Kingdom are already calling for the government to take a more active role in regulating food additives. Although I think the results of this most recent study do call for individuals to be more careful about what foods they and their children consume, at this point I do not think there is enough evidence for governments to make any kind of strict regulations concerning additives. The fact that the study only focused on children leaves open the possibility that additives may not affect adults at all, especially since the younger children were more affected than the older ones. In addition, the high individual differences in sensitivity to the additives calls into question the wisdom of the government regulating foods that may be perfectly harmless even for some children. At this point, I think the only role the government should play is to make sure all additives are listed in food ingredients so that consumers can make informed choices and to fund more research on the subject.