Gender Differences in Youth Externalizing Comorbidity

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This dissertation examined gender differences in youth externalizing comorbidity via three studies. Study 1 was a meta-analytic review that provided the first robust estimate of gender differences in youth externalizing comorbidity. Studies 2 and 3 unpacked these gender differences at two levels of analysis: personality (Study 2 and 3) and hormones (Study 3). Hypotheses for gender differences were guided by predominant theories, such as the gender paradox, gender intensification, and sexual selection theory. Both, these predominant theories and the limited prior studies on gender differences, generally suggested higher rates of comorbidity in externalizing girls than boys. Study 1 was a meta-analytic review of gender differences in youth externalizing comorbidity that was able to test these hypotheses and provided the first unbiased descriptive information regarding gender differences. This meta-analysis of epidemiological studies that conceptualized psychopathology categorically showed no evidence of gender differences in odds for experiencing comorbidity between oppositional defiant disorder (ODD) or conduct disorder (CD) and internalizing disorders. Having an externalizing disorder also increased the odds of having another disorder similarly across the genders. In addition, being a girl was associated with lower odds of experiencing comorbidity within externalizing disorders (e.g., attention deficit/hyperactivity disorder (ADHD)-ODD, ADHD-CD, ODD-CD) and lower odds of experiencing comorbidity between ADHD and internalizing disorders such as depressive and anxiety disorders. Age consistently accounted for externalizing-anxiety comorbidity rates in girls only, such that these comorbidity rates increased with age for girls. Thus, fewer gender differences were found in the meta-analysis than would be predicted by predominant theories. In fact, when gender differences were found, they were often in the direction opposite to the prediction, e.g., being a girl was associated with lower odds of comorbidity between ADHD and anxiety disorders. Study 2 tested whether child personality accounted for ODD comorbidity patterns more strongly in girls than boys in line with prior findings that girls need more risk factors than boys for the expression of other externalizing disorders. Participants in Study 2 were 346 children (49% boys; Mage = 9.97 years, SDage = 0.83 years) and their parents. Both parents reported on their child’s psychopathology symptoms and temperament/personality traits via questionnaires. One parent and the child also reported on the child’s psychopathology via structured clinical interview. Thus, I was able to conceptualize psychopathology dimensionally using symptom-counts. ODD comorbidity with externalizing disorders (i.e., CD and ADHD) was generally accounted for by variance in agreeableness and conscientiousness, whereas internalizing disorder comorbidity (i.e., depression and anxiety) was accounted for by variance in neuroticism. Gender moderation was largely absent. The overall lack of gender-specific results suggested that personality traits seem to be equally relevant for explaining boys’ and girls’ manifest ODD behaviors. Finally, Study 3 extended the nomological network of a bifactor model of psychopathology, a modern conceptualization of psychopathology and comorbidity, and neuroticism, by examining gender differences and associations with cortisol reactivity. For Study 3, mothers and their 349 primarily 9-to-10-year-old children (53% girls) were interviewed about the child’s psychopathology and mothers completed questionnaires about the child’s psychopathology and dispositional traits. Cortisol reactivity was measured while children performed a standardized laboratory stress task. This study found (1) partial support for gender invariance of the bifactor models of psychopathology and neuroticism, (2) mean level differences only on a specific fear factor (higher scores for girls), (3) gender moderation only of the specific irritability—externalizing association (stronger in boys), and (4) a significant association between the specific externalizing factor and low cortisol reactivity. As such, Study 3 also showed limited evidence for consistent gender differences in a bifactor model of psychopathology and the factors’ associations with neuroticism and cortisol reactivity. Across studies, theoretical and clinical implications were discussed, especially regarding the lack of support for existing gender theories, publication bias as a possibility for prior study’s significant findings regarding gender differences, and the importance of personality in assessment of psychopathology for both boys and girls.

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  • 03/07/2019
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