Are childhood externalizing disorders the harbinger of early-onset alcohol dependence?

BACKGROUND & OBJECTIVES The subtyping of alcohol dependence (AD) into early-onset (EO) and late-onset (LO) subgroups has been shown to have clinical and biological validity. As externalizing disorders (EDs) predate AD, the link of ED with age of onset of alcohol dependence needs to be investigated. The aim of this study was to examine the relationship of EDs such as disruptive behaviour disorder (DBD) and attention deficit hyperactivity disorder (ADHD) with age at onset of AD in a sample of male subjects. METHODS One hundred consecutive male subjects with AD presenting to the De-Addiction Services and an equal number of biologically unrelated non-substance-dependent control subjects were included in the study. The AD subjects were divided into EO (age of onset of AD ≤25 yr; n = 21) and LO (age of onset of AD >25 yr; n = 79). Subjects were examined for evidence of DBD and ADHD in childhood, and current ADHD using structured instruments such as Semi-Structured Assessment for the Genetic of Alcoholism-IV (SSAGA-IV) and Kiddie - SADS - Present and Lifetime Version (K-SADS-PL). The odds ratio of association of EDs with EO and LO AD was calculated by comparing these subgroups with the biologically unrelated control group. Later, both the subgroups of alcohol dependence were compared for the presence of EDs. RESULTS All EDs (DBDs/childhood or adult ADHD) were more common in AD individuals as compared to the controls. However, when AD subgroups were compared with controls, the association of DBDs and ADHD reached a significant level only in the EO subgroup. A comparison of EO and LO AD showed that more EO individuals had history of both childhood disruptive disorder and ADHD compared to LO subgroup. Adult ADHD was also over-represented in EO subgroup. INTERPRETATION & CONCLUSIONS Our study showed more EDs in alcohol dependent individuals compared to controls. Further, the association observed between EDs and EO alcohol dependence points towards a developmental continuum between these two conditions.