Long-Term Correlates of Attention Deficit Hyperactivity Disorder: A Meta-Analysis

Article excerpt

Studies link childhood Attention Deficit Hyperactivity Disorder (ADHD) to later risky behaviors, but do not indicate the likelihood of these problems occurring. This meta-analysis combines findings from 20 studies (34 correlations) of long-term outcomes including alcohol misuse, illegal drug use, general substance use, criminal behavior, and antisocial personality. All correlations except that with illegal drug use are significant, but average correlations are small (.12, .15) to medium (.17, .22), and may change with age. Thus, although ADHD is related to increased risk, the relationship is not strong. Promising preventions include parent education and early diagnosis and treatment.

In our roles as human science professionals, we sometimes have parents come to us with questions we find difficult to answer. For example, "My child has been diagnosed with ADHD, what does this mean for her future?" We want to be reassuring, but are aware of studies that link childhood Attention Deficit Hyperactivity Disorder (ADHD) with problems in adolescence and adulthood. How do we answer parents honestly and accurately? We need not only a summary of the literature, but also analyses that tell us how likely these outcomes are.

Much of the existing literature concerning the long-term influence of ADHD on the lives of those who have the disorder and their families examines risk-taking behaviors. For example, studies suggest that children with ADHD are more likely than those without the disorder to experience substance abuse and legal troubles as adults (Barkley, 1998). Individual studies give little information, however, on the relative importance of ADHD in predicting a child's life course. This study addresses this problem by investigating long-term outcomes for children with ADHD, using meta-analysis.

Meta-analysis enables one to derive conclusions from a body of literature by locating known published studies and combining them, as if into one big study. Emphasis is given to how strong the relationship is between two variables, whereas traditional statistical tests focus more on statistical significance. The relationship between two variables can be highly significant without being very strong (e.g., when the sample size is huge). When examining long-term outcomes, the strength of the relationship is more important than its significance (Schmidt, 1996).

A review of general information that has been presented about ADHD outcomes is provided in this article, followed by a meta-analysis of research on the links between ADHD and five specific outcomes. Finally, the implications of these analyses for families and clinicians is discussed.

ADHD is "the most commonly diagnosed behavioral disorder of childhood, estimated to affect 3 to 5 percent of school-age children" (Diagnosis and treatment, 1998). The disorder frequently continues into adolescence and adulthood (Barkley, 1997, 1998; Biederman, Faraone, Mick, & Spencer, 1995; Dalteg & Levander, 1998; Hechtman, 1991; Weiss, 1990), with 2% to 7% of adolescents and young adults affected (Practice parameters, 1997). ADHD tends to cluster in families. When one family member has ADHD, more than half of the time another close biological relative also will have its symptoms (Biederman et al., 1995; Evans, Vallano, & Pelham, 1994; Teeter, 1998). When ADHD is present in a family, it is commonly linked to increased stress, fewer resources, and limited coping skills.

Several researchers who have examined outcomes for children with ADHD into adolescence and adulthood have reported behavior problems, substance abuse, contact with police and courts (Barkley, 1998), in addition to academic, social, and emotional difficulties during adolescence (Hechtman & Weiss, 1983). Hechtman and Weiss (1983) reported that problems persisted into young adulthood for the majority, with a lesser but still troubling number experiencing severe psychiatric or antisocial problems. …