Subtypes of alcohol dependence in a nationally representative sample

Abstract

Objective

The authors sought to empirically derive alcohol dependence (AD) subtypes based on clinical characteristics using data from a nationally representative epidemiological survey.

Method

A sample of 1484 respondents to the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) with past year AD was subjected to latent class analysis in order to identify homogeneous subtypes.

Results

The best-fitting model was a five-cluster solution. The largest cluster (Cluster 1: ∼31%) was comprised of young adults, who rarely sought help for drinking, had moderately high levels of periodic heavy drinking, relatively low rates of comorbidity, and the lowest rate of multigenerational AD (∼22%). In contrast, Clusters 4 and 5 (∼21% and 9%, respectively) had substantial rates of multigenerational AD (53% and 77%, respectively), had the most severe AD criteria profile, were associated with both comorbid psychiatric and other drug use disorders, lower levels of psychosocial functioning, and had engaged in significant help-seeking. Clusters 2 and 3 (∼19% each) had the latest onset, the lowest rates of periodic heavy drinking, medium/low levels of comorbidity, moderate levels of help-seeking, and higher psychosocial functioning.

Conclusion

Five distinct subtypes of AD were derived, distinguishable on the basis of family history, age of AD onset, endorsement of DSM-IV AUD criteria, and the presence of comorbid psychiatric and substance use disorders. These clinically relevant subtypes, derived from the general population, may enhance our understanding of the etiology, treatment, natural history, and prevention of AD and inform the DSM-V research agenda.

Introduction

Alcohol dependence (AD) is a complex, common disorder that arises as the consequence of biological, behavioral, and environmental factors. For more than 150 years, the heterogeneity of individuals with AD has been recognized by both clinicians and researchers (Epstein, 2001). Efforts to classify individuals with AD into subtypes have been motivated by the pragmatics of clinical management (Jellinek, 1960, Lesch et al., 1988), recognition of the influences of family history and comorbidity on manifestations of AD (Babor et al., 1992, Cloninger et al., 1981, Schuckit, 1985), a life-course perspective that emphasizes long-term prognostic outcomes (Jacob et al., 2005, Lesch et al., 1988, Vailant, 1983, Zucker, 1987), and attempts to elucidate the complexity of genetic and environmental influences on the biopsychosocial etiology of the disorder (Bucholz et al., 1996, Cloninger et al., 1981, McGue, 1999).

These extant approaches to AD subtyping have employed either empirical or clinical/observational strategies using data derived primarily from treatment-seeking samples. This is a significant limitation, since sample size and attributes influence typological solutions. Recent data from the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) suggest that, among those with prior-to-past year AD, only 25.5% have ever received treatment (Dawson et al., 2005). Thus, there is a substantial proportion of the AD population that is not represented in the clinical samples previously used for typology development. Consistent with Berkson's bias (Peritz, 1984), sole reliance on hospitalized or treatment AD cases for subtype development may introduce a form of selection bias wherein only those cases that manifest greater severity or have clinical features associated with treatment program admission are accounted for in the typology. The resultant subtypes may not generalize well to the broad spectrum of community-dwelling AD individuals, thereby diminishing the utility of the typology for public health initiatives involving screening, early identification, treatment planning, or prevention.

Consequently, the purpose of this study is to empirically subtype those with current AD based upon a multivariate panel of dichotomous and dimensional clinical indicators, and using a nationally representative epidemiological sample obtained through the NESARC survey. We know of no other existing AD typology that is based upon nationally representative data, and that includes individuals both in and not seeking treatment who meet DSM-IV criteria for AD. This subtyping effort expands on prior research not only by using the DSM-IV criteria for alcohol use disorders (AUD), but also by including age of drinking onset, age of onset of AD, family history of AD in various configurations, the lifetime presence or absence of specific externalizing and internalizing psychiatric disorders, and other substance use disorders that are salient features of extant typologies.

This study is timely because the research agenda for DSM-V is currently being mapped out (Kupfer et al., 2002). By describing the clinical characteristics of disparate subgroups of individuals in the general population with AD, we hope to generate hypotheses that may stimulate changes in the diagnostic criteria for the next version of the psychiatric classification system. However, the clinical utility of any diagnostic typology relates not only to its capacity to aggregate clinical features into relatively homogeneous subgroupings as we report here, but also to guide treatment modality selection, predict treatment outcome, and prognosis. This report focuses on the initial objective of clinical categorization and its description; the latter therapeutic and prognostic objectives are beyond the scope of this current investigation, but will be addressed when data from the NESARC follow-up are available.