We found that children with ADHD “uncomplicated” by conduct disorder are at significantly increased risk for later criminality, as measured by arrests, convictions, aggressive offenses, felony charges, and incarcerations (), but only if they develop an antisocial or substance use disorder in adolescence. Indeed, children with ADHD who had not developed either disorder had similar rates of criminality to those of non-ADHD comparisons. Several follow-up studies have established that children with ADHD are at increased risk for conduct and antisocial personality disorders (Gittelman et al., 1985
; Mannuzza et al., 1991
; Weiss & Hechtman, 1993
; Biederman et al., 1996
; Barkley et al., 2004
). In addition, we reported, in two independent cohorts and for both probands and comparisons, that individuals with both CD and SUD invariably develop CD before (84%), or around the same time as SUD (16%) (Gittelman et al., 1985
; Mannuzza et al., 1991
). The present study extended these findings by examining age at first arrest. Since probands had ADHD in the absence of childhood CD, the present results describe a developmental cascade from childhood ADHD, to adolescent antisocial disorder, to substance abuse, and on to criminality. It seems important to attempt to break this chain of events by preventing the development of adolescent antisocial disorder in children with ADHD.
Since oppositional defiant disorder (ODD) was not an exclusion for children with ADHD, it could be argued that ODD increased their risk for CD, as some theories predict (Lahey et al., 2000
); in turn, CD increased risk for later criminality. In an earlier report on this sample, we examined the relationship between ODD and CD behaviors in childhood (as measured by parent and teacher ratings) and CD in adolescence. We found that ODD childhood behavior ratings did not predict clinically diagnosed, adolescent CD, but even very low levels of CD-type childhood problems did (Mannuzza et al., 2004
). Therefore, in this sample of prospectively followed, children with ADHD, but without clinically diagnosed, childhood CD, ODD childhood behaviors were not a developmental precursor to later CD, but childhood ADHD was.
In addition to rates of judicial events, ADHD probands were also more often arrested, convicted, and incarcerated than comparisons without childhood ADHD (). Indeed, among those arrested, fewer than half as many probands than comparisons had been arrested only once (25% vs. 64%, P = 0.002), and some probands were arrested 20-30 times. However, groups did not differ on age at first, or age at most recent, judicial contact (). Half of arrested probands and 68% of comparisons had their first encounter with the criminal justice system in adulthood (ns).
Several theories of ADHD are consistent with the finding that ADHD increases the risk for antisocial disorders and criminal behaviors. For example, over a century ago, George Still’s theory of defective moral control and, later, Paul Wender’s theory of minimal brain dysfunction, gave a principal role to the concept of poor inhibition (Barkley, 1999
). More recently, Herbert Quay’s theory of behavioral inhibition and Edward Sonuga-Barke’s work on impulsivity and delay aversion have emphasized inhibitory deficits associated with ADHD (Barkley, 2006
). Perhaps the most comprehensive model of ADHD is Russell Barkley’s theory of self-regulation. Barkley proposes a developmental-neuropsychological model of human self-control which implicates the significance of prefrontal lobe function. According to this theory, there is a delay between an event and a reaction (behavioral inhibition), and during this time lag, “executive functions” are initiated which, in concert, produce self-regulation and, consequently, goal-directed, appropriate behaviors that are more governed by long-term, than short-term or immediate outcomes. ADHD is characterized by a deficit in the inhibitory processes which, in turn, disrupt the development of the executive functions and adaptive behaviors they permit (Barkley, 2006
). It is beyond the scope of this article to review studies which support or refute this and other theories. Our purpose is to indicate that several theories predict that ADHD increases risk for later antisocial activities, and that gaining a better understanding of the underlying mechanisms of ADHD may aid in the development of intervention and prevention programs.
A limitation of the study is that about one-third of subjects from each group were not included since their residence during the follow-up interval could not be determined. It is encouraging that the proportion of subjects “lost to follow-up” was the same for both groups, and that arrest history analyses based on all 207 probands and 178 comparisons showed the same major findings presented in the current report. Also, there seems to be no reason to suspect that the relationship between proband-comparison arrest histories was different for subjects who were not included, compared to subjects who were included. Finally, our findings are consistent with those from our previous report in which the residential status of all subjects was known (Mannuzza et al., 1989
A second limitation is that criminal records were restricted to New York State, and that only subjects who resided in New York State throughout the follow-up interval were included in the analyses. The issue concerns whether the arrest histories of subjects who move out of state are systematically different from those of subjects who do not, and whether probands and comparisons are differentially characterized by this in-state/out-of-state relationship. For example, what if comparisons (but not probands) were more likely to be arrested for crimes committed out of state than in state? Then, by excluding subjects who moved out of state, the findings would be biased. We believe that such a relationship is remote, and are comforted by the findings that in-state and out-of-state probands and comparisons did not differ on any demographic variable.
It is also possible that differences other than childhood ADHD contributed to the development of later criminality. Since comparisons were not recruited in childhood, contemporaneous information was not available. Also, not all potentially relevant childhood variables (e.g., environmental traumas) were systematically studied in probands. However, the fact that probands and comparisons were identified from the same geographic regions (i.e., they lived in the same neighborhoods, attended the same schools, etc.) and were comparable in age and socioeconomic status when recruited in adolescence, diminishes the chances that childhood factors other than ADHD were of overriding significance to the groups as a whole.