Externalizing spectrum or spectra? Underlying dimensions of the externalizing spectrum

Background: Major psychiatric disorders have been conceptualized to comprise of two dimensions namely, the internalizing and externalizing spectrum. Externalizing spectrum disorders consist of childhood disruptive behaviour disorders (DBD), antisocial personality disorder (ASPD) and substance use disorders. They are supposed to share common underlying personality traits. However, there is a need to explore the underlying dimensionality of externalizing spectrum of both disorders and traits in a mixed clinical and nonclinical sample from a non-western cultural-ethnic backdrop.

Materials and methods: One hundred consecutive subjects with alcohol dependence (AD) and an equal number of biologically unrelated non-substance-dependent control subjects were recruited for the study. Subjects were examined for evidence of DBD and ASPD using Semi-Structured Assessment for Genetics of Alcoholism (SSAGA-IV). Validated instruments were used for the assessment of impulsivity, sensation seeking and hostility. Continuous scores generated from these instruments were converted to standardized Z scores to ensure comparability among different types of scales. Data were tested for normality of distribution by Kolmogorov-Smirnov test. Analysis was done by using principal component factor analysis with varimax rotation.

Results: Factor analysis revealed two broad factors underlying the externalizing spectrum. The first factor included conduct, antisocial personality and oppositional defiant disorder. This factor was labelled as disruptive-dissocial. The second factor, which included AD and all personality traits, was labelled as impulsive-hostile.

Conclusion: Within the externalizing spectrum, there are at least two distinct underlying dimensions: disruptive-dissocial and impulsive-hostile. If confirmed in other samples as well, this may have important implications for understanding and managing psychiatric and psychological issues.