ADHD and the externalizing spectrum: direct comparison of categorical, continuous, and hybrid models of liability in a nationally representative sample

Abstract

Purpose: Alcohol use disorders, substance use disorders, and antisocial personality disorder share a common externalizing liability, which may also include attention-deficit hyperactivity disorder (ADHD). However, few studies have compared formal quantitative models of externalizing liability, with the aim of delineating the categorical and/or continuous nature of this liability in the community. This study compares categorical, continuous, and hybrid models of externalizing liability.

Method: Data were derived from the 2004-2005 National Epidemiologic Survey on Alcohol and Related Conditions (N = 34,653). Seven disorders were modeled: childhood ADHD and lifetime diagnoses of antisocial personality disorder (ASPD), nicotine dependence, alcohol dependence, marijuana dependence, cocaine dependence, and other substance dependence.

Results: The continuous latent trait model provided the best fit to the data. Measurement invariance analyses supported the fit of the model across genders, with females displaying a significantly lower probability of experiencing externalizing disorders. Cocaine dependence, marijuana dependence, other substance dependence, alcohol dependence, ASPD, nicotine dependence, and ADHD provided the greatest information, respectively, about the underlying externalizing continuum.

Conclusions: Liability to externalizing disorders is continuous and dimensional in severity. The findings have important implications for the organizational structure of externalizing psychopathology in psychiatric nomenclatures.

Fig. 1

The constrained latent trait model in women and men (Model 2). Values presented on the structural paths from externalizing to the disorders are standardized factor loadings; values presented in boxes are thresholds (all significant p < 0.001). Values before the slash and in bold relate to women; values after the slash relate to men. ASPD antisocial personality disorder, Nic nicotine dependence, Alc alcohol dependence, Marij marijuana dependence, Coc cocaine dependence, Sub other substance dependence, ADHD attention-deficit hyperactiv-ity disorder. Arrows without numbers indicate unique variances, including error

Fig. 2

Response functions of externalizing disorders under a latent trait liability model (Model 2: constrained model)

Fig. 3

Information functions of externalizing disorders under a latent trait liability model (Model 2: constrained model)