Further evidence of differences in substance use and dependence between Australia and the United States

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Abstract

The current study compared the prevalence of substance use and DSM-IV dependence in the USA and Australia. Participants aged 18–54 were selected from two cross-sectional nationally representative Australian (National Survey on Mental Health and Well-Being – NSMHWB, 1997, n = 7570) and American (National Epidemiologic Survey on Alcohol and Related Conditions – NESARC, 2001–2002, n = 29,673) household surveys. The NSMHWB utilised the Composite International Diagnostic Interview, whereas the NESARC used the Alcohol Use Disorder and Associated Disabilities Interview Schedule. The 12-month prevalence of alcohol use was lower in the USA (56.5%) than in Australia (77.2%), although the rates of alcohol dependence were similar in both countries. The USA had higher rates of alcohol dependence conditional on use (9.0%) compared to Australia (6.8%). Australians had higher levels of drug use, dependence, and conditional dependence than Americans (except for sedatives and opioids). The absence of significant interactions between country of interview and the common correlates of substance use disorders indicated that the influence of these factors was similar in the USA and Australia. In conclusion, the current investigation revealed striking differences in the rates of conditional drug dependence between Australia and the USA. The cross-national generalizability of the relationships between the common correlates and prevalence of substance use and dependence indicates that a similar process of vulnerability to dependence may be operating in the USA and Australia. In the future, these cross-national differences could be used to help better understand the factors that influence drug use and the development of dependence.

Introduction

Recent epidemiologic surveys have demonstrated that the use of, and dependence on, licit and illicit substances is widespread in Westernised societies (Andrews et al., 2001, Compton et al., 2007, Hasin et al., 2007), increasing in lower-income countries (Anderson, 2006, Hall and Degenhardt, 2007), and resulting in worldwide substantial economic and societal costs (Hasin et al., 2007). National epidemiologic surveys are essential in understanding the prevalence and correlates of psychiatric conditions, including drug and alcohol dependence (Caetano and Babor, 2006, Teesson et al., 2006). Over the last two decades, descriptive psychiatric epidemiology has undergone an unprecedented period of growth (Cottler et al., 1991, Kessler, 2007, Tsung and Tohen, 2002) yet there are still very few cross-national comparisons.

Studies indicate that approximately 48% of the global population are current consumers of alcohol, whereas 4.5% are current users of illicit drugs (Anderson, 2006). However, there is substantial variation in prevalence estimates of substance use and associated disorders both within countries (Compton et al., 2007, Grant et al., 2004), and between different countries of relatively similar socio-economic status (Maxwell, 2003, Teesson et al., 2006, Vega et al., 2002). For example, comparative data analysis of recent American epidemiologic surveys, namely the National Comorbidity Survey Replication (NCS-R; Kessler et al., 2004), the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC; Grant et al., 2003a), and the National Survey on Drug Use and Health (NSDUH; SAMHSA, 2003), has demonstrated numerous discrepancies in prevalence rates for drug use and associated disorders between the surveys, which could in part be attributed to differences in methodological design (Grucza et al., 2007, Grant et al., 2007). Indeed, non-comparable survey designs and protocols are not only problematic when conducting within-country comparisons, but these differences are often magnified and can greatly hinder between-country comparisons (Vega et al., 2002). Nevertheless, with proper interpretation of methodological differences, cross-cultural epidemiological comparisons are important to better understand the use of specific drugs in different countries, the associations of use with different socio-demographic variables, as well as providing possible clues regarding the etiology of substance use disorders (Canino et al., 1999, Kessler et al., 1997, Smart and Ogborne, 2000, Vicente et al., 2006). Reliable and valid cross-national psychiatric epidemiologic comparative studies however can be very time-consuming, requiring substantial financial costs and professional resources (Heeringa et al., 2004). Thus, it is not surprising that few cross-country comparisons are conducted (Teesson et al., 2006).

In an attempt to overcome these obstacles, a small number of cross-cultural studies have been conducted in recent years. For example, Maxwell, 2001, Maxwell, 2003 compared data from the 1995, 1998, and 2001 Australian National Drug Strategy Household Surveys and the United States National Household Surveys on Drug Abuse. After taking into account a variety of methodological differences between the two surveys (e.g., wording of questions, data collection method, and the age of participants), these studies revealed key differences in the prevalence and trends of substance use between the U.S. and Australia. Specifically, the results demonstrated that although rates of lifetime and past-year illicit drug use was highest among Australians in their twenties, rates of lifetime drug use in Americans was highest among individuals in their thirties and forties and the highest rates of past-year substance use was among American teenagers (Maxwell, 2003). Similarly, Teesson et al. (2006) assessed differences in the prevalence and correlates of substance use and dependence between Australia and the USA using age-matched samples from two well-known epidemiologic surveys, the 1997 Australian National Survey on Mental Health and Well-Being (NSMHWB; Australian Bureau of Statistics, 1998) and the 1990–1991 National Comorbidity Survey (NCS; Kessler et al., 1994). The results suggested that alcohol use was higher in Australia than in the USA, but that rates of conditional alcohol dependence (i.e., dependence among users) were relatively similar in both countries. Although rates of other drug use were relatively similar in both countries, rates of substance dependence and conditional dependence were higher in Australia than in the USA. These findings were significant because they suggested that a variety of country-specific factors (e.g., availability of drugs, cultural influences, or social factors) could have impacted on the prevalence of substance dependence. However, one confounder of the study was that the U.S. data was collected in the early 1990s almost 7 years before the Australian data. It was unclear therefore whether the results represented true differences between the countries or simply reflected changes in the epidemiology of drug use across time.

More recent U.S. epidemiologic data has identified changes in patterns of substance use and associated disorders in surveys conducted in the decade following the NCS. Throughout the 1990s and into the early 21st century, the past-year prevalence in the USA of non-medical prescription drug use and use disorders increased by 50% and 67%, respectively (Blanco et al., 2007). Comparison of data from the 1991–1992 National Longitudinal Alcohol Epidemiologic Survey (NLAES; Grant et al., 1994) and the 2001–2002 NESARC (Grant et al., 2003a) has produced some noteworthy findings. For example, during this time it appears that cannabis use in the USA did not significantly increase; however, cannabis dependence increased from 0.3% to 0.4% (Compton et al., 2004). Moreover, during the same time period, although the percentage of regular drinkers increased from 44.4% to 51.2% (Dawson et al., 2004), the prevalence of alcohol dependence significantly decreased (Grant et al., 2004).

Clearly, changes appear to have occurred in the prevalence and patterns of use of a range of drugs in the United States over the last number of year. The aim of the current study is to advance on the previous work of Teesson et al. (2006) and to examine whether analyzing more recent epidemiological data from the United States would reveal different contrasts in patterns of substance use and associated disorders between the USA and Australia. The present study used data on the 12-month DSM-IV prevalence of alcohol and drug use disorders in the USA population, as derived from the NESARC (2001/2002), and compared these findings to Australian data from the NSMHWB (1997). Not only are the surveys closer in time than previous comparisons but this time the U.S. data is more recent than the Australian data.

Section snippets

Sample

The current study mainly focuses on two epidemiologic surveys: the 1997 NSMHWB (Australian Bureau of Statistics, 1998), and the more recent 2001–2002 NESARC (Grant et al., 2003a). For comparative purposes, prevalence estimates from the NCS (Kessler et al., 1994) that were derived from a recent cross-national investigation (Teesson et al., 2006) are also presented. Although the NSMHWB and the NESARC have been described in detail elsewhere (Andrews et al., 2001, Grant et al., 2004), they will be

Prevalence of substance use in the past 12 months

The demographic characteristics of the sub-samples used from the NSMHWB and the NESARC are displayed in Table 1. The 12-month prevalence rates for substance use, dependence, and conditional prevalence in Australia and the USA are presented in Table 2. For comparative purposes, data from the NCS that was derived from a previous investigation (Teesson et al., 2006) is also displayed. An initial noteworthy finding is that the prevalence of substance use (except sedative use) differed significantly

Discussion

Previous research suggested that Australians interviewed in 1997 reported higher levels of drug use and dependence, particularly in relation to cannabis, compared to their American counterparts in 1990–1991 (Teesson et al., 2006). This research was informative but it was unclear whether true differences existed, or whether they also reflected changes in patterns of drug use and dependence during the 1990s. Thus, in an attempt to advance the literature, the current investigation explored whether

Role of funding source

The design, development, and conduct of the National Survey of Mental Health and Well-Being (NSMHWB) was funded by the Mental Health Branch of the Commonwealth Department of Health and Family Services. The National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) was sponsored and conducted by the National Institute on Alcohol Abuse and Alcoholism (NIAAA), with supplemental support from the National Institute on Drug Abuse.

Contributors

Orla McBride contributed to the conception and design of the paper, conducted the statistical analysis, and drafted the manuscript. Maree Teesson and Tim Slade contributed to the conception and design of the paper, oversaw the statistical analysis, and provided critical revisions of the manuscript. Deborah Hasin, Louisa Degenhardt and Andrew Baillie provided critical revisions of the manuscript. All authors have contributed to and approved the final manuscript.

Conflicts of interest

None.

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