Attention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed disorders in childhood. In fact, estimates of the rates of ADHD had found that between 5-10 percent of all children meet diagnostic criteria for the disorder. Children with and without ADHD, at a group level, show several differences, including poorer school performance, more peer rejection, and increased rates of anxiety, depression, and acting out behavior. Following children over time is a common way to study the long term effects associated with psychological problems. Many scientists have used follow-up (longitudinal) studies to examine whether children with ADHD are a greater risk for substance use and abuse/dependence than children without ADHD. Any single study may be imperfect, as studies differ in the way ADHD is measures, substance use or abuse/dependence is measures, the group of children that were followed, or how much time passed between the follow-up assessment. One way to help find clarity in multiple studies of the same question is to conduct a meta-analysis. Meta-analyses run one major analysis using all of the data collected using different groups – more heavily weighting the results from larger studies. Earlier this year, a meta-analysis on the association between a childhood diagnosis of ADHD and trying alcohol, tobacco, marijuana, as well as a substance use disorder (substance abuse or dependence/addiction) was conducted.
In all, 27 long-term studies that followed approximately 4,100 children with ADHD and 6,800 children without ADHD were included. Results indicated that children with and without ADHD are no different in their likelihood to try alcohol. In my opinion, this is likely due to the fact that most individuals try alcohol at some point in their adolescence. For all other outcomes, children with ADHD were at a greater likelihood of trying substances and abusing or becoming dependent on substances. Results were presented using odds ratios, which is a measure of effect size. If an odds ratio (OR) = 2, then one group is twice (2 times) as likely to have the particular outcome. In the present study comparing children with and without ADHD, the OR for ever smoking was over 2, and for every trying marijuana it was 2.78. For substance use disorders, the ORs were nearly 3 for nicotine dependence, 1.74 for alcohol abuse/dependence, around 1.5 for marijuana abuse/dependence, and over 2 for cocaine abuse/dependence.
So, does this mean that a child with ADHD is going to try and/or abuse substances. Not necessarily. All of the studies looked at group differences, so there were many children with ADHD who never touched a substance, and several children without ADHD who later became substance dependent. The next question to ask is why children with ADHD are at greater risk. Perhaps understanding what factors increase vulnerability to substance initiation or abuse/dependence will help researcher and practitioners identify children who would benefit most from targeted substance use prevention programs.
To read more about the ADHD and Development Lab, please visit to the website.