Article Analysis: “Axis I and II Comorbidity in Adults with ADHD”

The scholarly journal article entitled “Axis I and II Comorbidity in Adults with ADHD” written by Miller, Nigg, and Faraone (2007) was written with the aim of studying attention deficit hyperactivity disorder (ADHD) and possible Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) comorbidities in the adult population. According to the authors, adults with ADHD are rarely studied as most research focuses predominantly on small samples of male children. Because many adults who suffered from ADHD as children experience negative outcomes like lower education levels, impaired employment opportunities, substance abuse addictions, and increased risk for incarceration, the authors believe that research on ADHD comorbidities is warranted. Specifically, Miller et al. (2007) sought to explore if ADHD-I exhibits less externalizing problems than ADHD-C and if Axis II personality disorders have any correlation with ADHD disorder.

The study revealed unexpected findings. Although the team had gone to great lengths to ensure females with ADHD would be proportionate in the sample, the males significantly outnumbered the females. The team noted that this finding could have occurred because past research suggests more males than females suffer from ADHD in the general population. The team also discovered that ADHD-C participants had a fivefold risk compared to the ADHD-I group for two or more externalizing disorders like substance abuse, obsessive-compulsive disorder, and antisocial disorder. Regarding internalized disorders like anxiety, the ADHD-C group also had higher rates than the ADHD-I group. Additionally, the research analysis revealed that the ADHD groups were all at much higher risk of having a borderline personality disorder, histrionic personality disorder, antisocial personality disorder and narcissistic personality disorder than the control subjects. Using regression analysis the findings revealed that borderline personality disorder in the ADHD group was a significant predictor that other Cluster B disorders would be present. Another unexpected finding was that ADHD women were much more likely than the ADHD men or the control groups to have Cluster B disorders with the female control group at 7.3% and the female ADHD group at 30.3%.  Regarding Axis II impairments, all of the ADHD participants with any of the 10 disorders were found to have significant impairments that could be reliably predicted using multiple regression and GAF scores. The research team concluded that ADHD Axis I indicates a propensity for personality disorders because ADHD likely lowers the individual’s threshold for self-control, frustration, anxiety, and ability to maintain attention.

There are many implications from this study for future research. First, because the sample was 86% Caucasian and the study found minority groups ranked as more likely to be diagnosed with ADHD comorbidities, there is a need for more research on African-American, Latino, and Asian populations from different socioeconomic groups. Secondly, the unexpected results that all of the ADHD adults had increased Cluster C personality obsessive-avoidant features compared to the control group warrants further investigation into possible physiological, genetic, and neurological causes. Treatment can include certain conditioning and CBT therapies. The also authors point out that their findings suggest that research should allow for differential diagnosis overlapping studies to avoid the traditional top-down hierarchy models used by psychologists.  A final implication for the study is inherent in the limitation of the Miller et al. (2007) findings that may have introduced bias into the results. Because the study used a retrospective cohort sample who were already adults, self-reporting had a high likelihood of being overly subjective. Larger samples should be used in future studies that include adults beyond the inclusionary selection of those who were between 18 and 37 years of age. The authors point out that future studies should follow ADHD children longitudinally into adulthood and base data on objective medical records.

Reference

Miller, T.W., Nigg, J.T., & Faraone, S.V. (2007). Axis I and II comorbidity in adults with ADHD. Journal of Abnormal Psychology, 116(3), 519-528.