1 Attention-Deficit/Hyperactivity Disorder and Aggression in Jamaican Students Scott W. Minor, Garth Lipps, Patricia Prescott, Doneisha Burke, Don-Marie Holder University of the West Indies, Mona Ganesh Shetty and Kathleen Lamb University of Technology, Mona Abstract The Government of Jamaica has targeted reduction of aggressive and violent behavior as a national priority. Recent research suggests that a childhood history of Attention-Deficit/Hyperactivity Disorder (ADHD) may be one intervening variable influencing the expression of adult aggressive and criminal behavior. Consistent with previous research in the United States, this present study found that both male and female college students, who were identified as ADHD on the Wender Utah Rating Scale, reported more physical aggression, anger and hostility. The results are consistent with contemporary theories of ADHD and aggression that focus on the importance of low self-control and difficulties with response inhibition. 13
2 ADHD and Aggression Attention-Deficit/Hyperactivity Disorder and Aggression in Jamaican Students The Government of Jamaica has targeted reduction of aggressive and violent behavior as a national priority and violence has recently been identified as a major health problem in Jamaica. In 1992, over 50% of admissions for trauma to the University Hospital of the West Indies were related to interpersonal violence (Meeks-Gardner, Powell & Grantham-McGregor, 2000). Further, the homicide rate in Jamaica increased from 17.6 per 100,000 in 1976 to 43 per 100,000 in 2001 and the homicide rate in the city of Kingston is one of the highest in the world (Harriott, 2003). Recent research suggests that a childhood history of Attention-Deficit/Hyperactivity Disorder (ADHD) may be one intervening variable influencing the expression of adult aggressive and criminal behavior (Minor, in press; Minor, Cottle & McElroy, 1998; Pratt, et al., 2002). Certainly, there are a number of other high risk factors associated with both ADHD and a history of aggressive behavior, including, poor academic performance, lower cognitive functioning, neuropsychological deficits, truancy and behavior problems (Barkley, 2001; Brown et al., 2001; Nadder et al., 2001). Although there has been little research in Jamaica addressing the relationship between ADHD and aggression, it has been found that the prevalence of symptoms of ADHD in Jamaican Primary school boys, but not Preparatory School boys, is substantially higher than that found in the United States (Minor, Cantrell & Floyd, 1997). Further, Samms-Vaughan (2000) found that children displaying attention, aggression and/or delinquency problems were more likely to have lower school performance and to perform worse on cognitive measures. There has been some longitudinal research assessing the comorbidity of ADHD and aggression in children and adolescents in the United States (see Satterfield, Swanson, Schell & Lee, 1994). The relationship between a childhood history of ADHD and antisocial behavior to adolescent and young adult criminal behavior and incarceration has been well established in both prospective (Babinski, Hartsough & Lambert, 1999; Satterfield, Swanson, Schell & Lee, 1994; Satterfield & Schell, 1997) and retrospective (Curran & Fitzgerald, 1999; Vitelli, 1998) studies. For example, prevalence rates for ADHD in adult male inmates have been reported to be from 25% (Eyestone & Howell, 1994) to 64% (Vitelli, 1998). More recently, Minor (in press) found that 38% of male inmates and 41% of female inmates met criteria for a diagnosis of ADHD. This higher than expected prevalence of ADHD in adult inmates seems to be predicated upon a comorbid history of childhood antisocial behavior and conduct disorder (Babinski, Hartsough & Lambert, 1999; Satterfield & Schnell, 1997). A possible mediating variable that may help explain the salience of childhood conduct problems among ADHD children in predicting adult criminal behavior
3 and incarceration may be aggression. For example, in a sample of 224 college students in the United States, Minor, Cottle & McElroy (1998) found that both male and female students who scored higher on the Wender Utah Rating Scale (WURS, Ward, Wender & Reimherr, 1993) scored higher on all measures of the Aggression Questionnaire (Buss & Perry, 1992): Physical Aggression, Verbal Aggression, Anger and Hostility. Also, Minor (in press) found that both male and female inmates who met the WURS cut off score for ADHD, reported more physical and verbal aggression and more anger and hostility. These results are consistent with Barkley s recent emphasis on the importance of difficulties with executive functions as being the major factor in understanding ADHD (Barkley, 2001). The purpose of the present study was twofold: (1) to replicate, with a Jamaican sample, the previously reported findings (Minor, in press; Minor, Cottle & McElroy, 1998) of higher levels of self-reported aggression among participants with higher scores on the WURS; (2) to examine the influence of gender on the relationship between ADHD and aggression. Method Participants The participants were 91 students, 36 men (mean age = 20.7) and 55 women (mean age = 20.3), who were enrolled in introductory classes at the University of Technology, Kingston, Jamaica. All participants volunteered to participate in the research and met in small groups to complete the following measures that were presented in counterbalanced order: the Wender Utah Rating Scale (WURS, Ward et al., 1993; Ward, 1995) and the Aggression Questionnaire (Buss & Perry, 1992). Measures The WURS measures symptoms of ADHD in adults by retrospectively establishing a childhood history of ADHD. The WURS is a widely used measure for assessing ADHD in adults. It consists of 61 statements answered on a 5-point scale from not at all to very much. In this research we used the 25 critical items that were found to correctly identify 96% of normal adult and adults with ADHD (Ward, Wender, & Reimherr, 1993). The WURS has been found to be a reasonably reliable measure. Minor, Cottle & McElroy (1998) reported that the WURS has reasonable levels of internal consistency reliability (alpha =.91). Scores on the WURS have also been found (Rossini & O Conner, 1995) to be temporally stable over a four-week period (r tt =.68). The Aggression Questionnaire (Buss & Perry, 1992) consists of 29 statements answered on a similar five-point scale. In addition to a score for Total Aggression, 15
4 ADHD and Aggression separate scores can be created for Physical Aggression, Verbal Aggression, Anger and Hostility. Previous research (Minor, Cottle & McElroy, 1998) found the total score and separate sub-scales of the Aggression Questionnaire to have acceptable levels of internal consistency reliability (Total Aggression,.94; Physical Aggression,.84; Verbal Aggression,.80; Anger,.82; and Hostility,.90). Buss & Perry (1992) report test-retest reliability, over a nine-week interval, of.80 for Physical Aggression,.76 for Verbal Aggression,.72 for Anger and.72 for Hostility. Procedure After signing a consent form, all participants met in small groups and completed the Aggression Questionnaire and WURS in a counterbalanced order. Results Both the WURS and the Aggression Questionnaire had acceptable levels of internally consistent reliability (0.88 for both the WURS and the Aggression Questionnaire). In addition, each of the sub-scales of the Aggression Questionnaire was reliable:.80 for Physical Aggression;.67 for Verbal Aggression;.70 for Anger and.82 for Hostility. Retrospective reports of symptoms of ADHD were moderately related to aggression. With the exception of Verbal Aggression, scores on the WURS were moderately correlated with Total Aggression (0.51), Physical Aggression (0.39), Anger (0.42), and Hostility (0.48). Symptoms of ADHD had a small relationship with Verbal Aggression scores (0.14). Participants were divided into ADHD and non-adhd groups using a median split procedure. A 2 by 2 MANOVA (ADHD type by gender) was conducted using the four sub-scales of the Aggression Questionnaire as dependent variables. A separate 2 by 2 ANOVA (ADHD type by gender) was conducted using the Total Scale of the Aggression Questionnaire as a dependent variable. To test the robustness of our analyses we replicated the analyses using the recommended cutoff score on the WURS. ADHD (Median Split) by Gender Results of the univariate ANOVA using ADHD group and gender as independent variables and total aggression scores as the dependent variable revealed a single main effect for ADHD type (F(1,87)= 11.97, p<.001; partial eta squared = 0.12). Students who scored above the median on the WURS reported significantly higher levels of aggression than students who scored below the median (Table 1). Neither the main effect for gender nor the interaction of ADHD type and gender were statistically significant (p >.05).
5 Table 1 Mean Scores for the Aggression Measures by ADHD (based on a median split) and Gender ADHD Non- ADHD Aggression Scales Males Females Males Females Total aggression Physical aggression Verbal aggression Anger Hostility Two significant main effects emerged from the 2 (ADHD) x 2 (Gender) MANOVA of the aggression sub-scales. First, a significant main effect for the retrospective measure of ADHD was found, (F(4,84)= 3.55, p<.01; multivariate effect size = 0.145). Inspection of the univariate ANOVAs following the MANOVA, suggest that differences between ADHD groups occurred on the Physical Aggression (F(1,87)= 11.27, p<.001;), Anger (F(1,87)= 8.93, p<.01), and Hostility (F(1,87)= 7.45, p<.01) sub-scales. Students with scores above the median on the WURS reported higher levels of aggression on each of these subscales (Table 1). No significant differences between ADHD groups were noted on the Verbal Aggression sub-scale (F(1,87)=1.88, p >.05). Second, gender had a significant main effect on students levels of aggression (F(4,84) = 5.84, p <.001; multivariate effect size = 0.218). Univariate ANOVAs following the MANOVA revealed that this was primarily due to differences in levels of physical aggression, (F(1,87) = 7.84, p <.01), with males scoring higher on the Physical Aggression subscale than females (Table 1). No significant gender differences were observed on the Verbal Aggression, Anger or Hostility sub-scales (all p values >.05). The interaction of ADHD type and gender was not statistically significant (F(4,84) = 0.63, p > 0.05; multivariate effect size = 0.029). ADHD (based on the recommended cutoff score) x Gender To test the robustness of our analyses, students were divided into ADHD and Non-ADHD groups using the prescribed cutoff scores recommended by Ward, Wender & Reimherr (1993). All analyses were then repeated. Consistent with the results for the median split approach, students who were classed as ADHD versus those who were classed as Non-ADHD significantly differed in terms of Total Aggression scores (F(1,87) = 21.31, p <.001; eta-squared = 0.20). Examination of Table 2 reveals that those students meeting the WURS cutoff score, reported higher scores on the Total Aggression Scale. Consistent with the findings of the 17
6 ADHD and Aggression median split analyses, both the gender main effect and the interaction of ADHD group and gender were non-significant for Total Aggression scores (p >.05). Table 2 Mean Scores for the Aggression Measures by ADHD (based on the WURS cutoff score) and Gender ADHD Non- ADHD Aggression Scales Males Females Males Females Total aggression Physical aggression Verbal aggression Anger Hostility As with the median split analyses, two significant main effects emerged from the 2 (ADHD Type) by 2 (Gender) MANOVAs of the aggression sub-scales. First, a significant main effect was found for ADHD Type (F(4,84) = 6.53, p <.001; multivariate effect size = 0.237). Univariate ANOVAs following the significant MANOVA main effect indicated that ADHD types differed on levels of Physical Aggression (F(1,87) = 14.71, p <.001), Anger (F(1,87) = 13.37, p <.001), and Hostility (F(1,87) = 19.69, p <.001). On each of these variables, students above the cutoff for ADHD reported higher levels of aggression. Verbal aggression did not appear to differentiate ADHD types (p > 0.05). Second, consistent with the median split analyses, gender appeared to play a significant role in students reports of aggressive behaviours. Results of the MANOVA found a statistically significant main effect for gender (F(4,84) = 4.86, p <.001; multivariate effect size =.188). Univariate ANOVAs following the multivariate test indicated that this gender difference occurred primarily on the Physical Aggression subscale (F(1,87) = 8.29, p <.01). Male students reported higher levels of physical aggression than female students. No significant differences between male and female students were observed on the Verbal Aggression, Anger, or Hostility sub-scales. In agreement with the median split analyses, ADHD type and Gender did not combine to influence students levels of aggression as indicated by the absence of a statistically significant ADHD type by Gender interaction in the MANOVA analysis (p>.05).
7 Discussion In general, the data are very consistent with similar research done in the United States (Minor, in press; Minor, Cottle and McElroy, 1998) suggesting that previous research in this area, based on populations in the United States, may be generalizable to Jamaican populations. Although men scored higher than women on measures of physical aggression, this was not found for the other aggression measures and, more importantly, gender did not interact with measures of ADHD for any of the aggression measures. Thus, the often-reported explanation that boys with symptoms of ADHD are more often referred for treatment because of aggression was not supported. On the other hand, both male and female students who exhibited more ADHD symptoms (based on a median split or cutoff score on the WURS), scored higher on measures of physical aggression, anger and hostility. These results are also consistent with the previously reported research done in the United States. However, the finding regarding verbal aggression is not consistent with the previous research done in the United States. Unlike Minor, Cottle and McElroy (1998), both male and female Jamaican students identified as ADHD, did not report more verbal aggression. Examination of Tables 1 and 2 reveal that the results were in the predicted direction, but did not approach significance. The differences in these results may be related to cultural differences in how feelings of frustration are verbally expressed in Jamaican people. The major results of this study are consistent with modern conceptualizations of ADHD (see Barkley 2001) and aggression and criminality (see Gottfredson & Hirschi, 1990). While Barkley describes impulsivity, and in particular, difficulties with response inhibition, as being the most important feature in ADHD, Gottfredson and Hirschi postulate the concept of low selfcontrol as being a salient variable in explaining aggressive and criminal behavior. Thus, consistent with current neuropsychological thinking, difficulties with executive functions may be the key variable in understanding both ADHD and aggression. If this is true, persons with ADHD, since they experience more feelings of aggression, may be at high-risk for having difficulty in controlling themselves and may act impulsively on these feelings that is, being behaviorally aggressive. This may not be true for physical aggression only, as ADHD persons would be predicted to be more likely to act on feelings of anger and hostility as well. There were a number of limitations to this study. First, the sample size was smaller than we had wanted and this limits generalizability of our results. Further research is now in progress to address this limitation. Secondly, the WURS does not allow for separate measures of inattention and impulsivity/hyperactivity. It could be predicted that the results found here may not generalize to populations scoring higher on inattentive measures, but not measures of impulsivity/hyperactivity. 19
8 ADHD and Aggression This is also the target of current research. Lastly, the participants in this research were university students. It may be that university students reporting high levels of ADHD symptoms are not directly comparable to adults diagnosed as meeting DSM-IV criteria for ADHD. There were some interesting gender differences found in this research that will be the focus of a separate paper. References Babinski, L., Hartsough, C. & Lambert, N. (1999). Childhood conduct problems, hyperactivity-impulsivity and inattention as predictors of adult criminal activity. Journal of Psychology & Psychiatry & Allied Disciplines, 40, Barkley, R. A. (2001). The executive functions and self-regulation: An revolutionary neuropsychological perspective. Neuropsychology Review, 11, Buss, A. & Perry, M. (1992). The aggression questionnaire. Journal of Personality and Social Psychology, 63, Brown et al. (2001). Prevalence and assessment of Attention- Deficit/Hyperactivity Disorder in primary care settings. Pediatrics, 107, Curran, S. & Fitzgerald, M. (1999). Attention-Deficit/Hyperactivity Disorder in the prison population. American Journal of Psychiatry, 156, 1,645-1,665. Eyestone, L. & Howell, R. (1994). An epidemiological study of attentiondeficit/hyperactivity disorder and major depression in a male prison population. The Bulletin of the American Academy of Psychiatry and the Law, 22, Gottfredson, M. & Hirschi, T. (1990). A general theory of crime. Stanford, CA: Stanford University Press. Harriott, A. (2003). Understanding Crime in Jamaica. Jamaica: University of the West Indies Press. Meeks-Gardner, J., Powell, C. & Grantham-McGregor, S. (2000). A case control study of family and school determinants of aggression in Jamaican children. Planning Institute of Jamaica. Minor, S. (in press). Attention-deficit/hyperactivity disorder, aggression and incarceration. The Santiago Review. Minor, S. Cantrell, C. & Floyd, S. (1997). Symptoms of ADHD in Jamaican boys. Paper presented at a meeting of the Southeastern Psychological Association. Minor, S., Cottle, C. & McElroy, L. (1998). The importance of aggression and gender in measures of ADHD. Paper presented at the Southeastern Psychological Association. Nadder, T., et al. (2001). Comparison of multiple measures of ADHD symptomatology: A multivariate genetic analysis. Journal of Child Psychology and Psychiatry and Allied Disciplines, 42,
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