tion and other disorders. For example, it adjusts the comorbidity between anxiety and depression for comorbidity between anxiety and ADHD and depression and ADHD. As the figure demonstrates, comorbidity is widespread, and there are clear patterns; there is greater comorbidity among disruptive behavior disorders, ADHD, and substance abuse disorders, on one hand, and among the emotional disorders (anxiety and depression), than between emotional and disruptive behavioral disorders, on the other. Comorbidity remains high from early childhood (Egger, Erkanli, et al., 2006) through adolescence (Roberts, Roberts, and Xing, 2007) and into adulthood (Kessler, Chiu, et al., 2005).

In summary, there is consistent evidence from multiple recent studies that early MEB disorders should be considered as commonplace as a fractured limb: not inevitable but not at all unusual. The prevalence of these disorders is the same in young people as it is in adults. An implication for prevention is that universal programs will not be wasted on large numbers of risk-free children.

IS PREVALENCE INCREASING OR DECREASING?

Repeated surveys are needed to tell whether rates of any disorder are going up or down. For adults, a second NCS has recently been completed, and should provide some information for the population ages 18 and older. The one area of problem behavior in which data on trends in young people are available is alcohol and other drug use and abuse. Three national surveys—NSDUH, the Youth Risk Behavior Surveillance System, and MTF—regularly measure alcohol and drug use and abuse in young people. All restrict their data collection to adolescents (12 and over for NSDUH, 8th, 10th, and 12th grade students for MTF). MTF tends to produce slightly higher estimates than NSDUH; however, they are remarkably consistent in their reports of trends, which show a clear reduction in use across nearly all categories between 2002 and 2007 (see http://oas.samhsa.gov/NSDUH/2k6NSDUH/2k6results.cfm#Tab9-1).

Reviews or meta-analyses have used cross-sectional studies conducted at different periods, together with the small longitudinal data sets available, to put together a picture over time (Collishaw, Maughan, et al., 2004; Costello, Foley, and Angold, 2006). Evidence of this sort has produced two fairly clear conclusions: there has been an increase in disruptive behavior symptoms over the past few decades (Collishaw, Maughan, et al., 2004), whereas there is no evidence for a similar increase in child or adolescent depression (Costello, Erkanli, and Angold, 2006). The question of whether the prevalence of autism has increased (Fombonne, 2005) is fraught with problems of broadening of the diagnostic category, heightened public awareness, and more attention from clinicians (Schechter and Grether, 2008). The same is true of



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