ReviewQuality of life among opiate-dependent individuals: A review of the literature
Introduction
Patients’ self-reported outcomes (e.g. quality of life) have become an increasingly important source of information in health care. This has been helped by a focus on the empowerment of help-seeking individuals (Segal, 1998) and the prevalence of various chronic illnesses (Guyatt et al., 2007, Smith et al., 1999). The limited curing effect of treatment services for chronic diseases such as diabetes and depression, for example, has created the need for long-term treatment and a shift from cure to care, with attention to the patients’ perspectives (Wiklund, 2004).
The best known patient-reported outcome is quality of life (QoL) (Valderas et al., 2008, Winklbaur et al., 2008). During the last decades various disciplines have focused on QoL (Bowling & Brazier, 1995), however, the concept is vague and its use inconsistent (Dijkers, 2007, Farquhar, 1995, Skevington et al., 2004, Smith et al., 1999). Researchers often consider terms like “health status” and “health-related quality of life” (HRQoL) as synonymous with QoL (Muldoon, Barger, Flory, & Manuck, 1998), resulting in the inconsistent use of the concept (Gill, Alvan, & Feinstein, 1994). HRQoL has its foundations in a definition of health from 1947 (Cummins, Lau, & Stokes, 2004) and this contrasts sharply with subjective well-being or subjective QoL. It measures the effects of a disease on individuals’ everyday functioning, with special attention given to physical and psychological limitations (Burgess et al., 2000). HRQoL is frequently used in general medicine to demonstrate the absence of pathology. In social sciences and psychiatry, on the other hand, there is a strong focus on respondents’ reported satisfaction with life as a whole, including a multidimensional or holistic approach to the concept of QoL (Cummins et al., 2004, Van Nieuwenhuizen et al., 2002). Several authors (Katschnig, 2006, Schalock and Verdugo Alonso, 2002) have demonstrated the importance of individuals’ own perceptions in conceptualising QoL and approach QoL as a “sensitising concept” – starting from individuals’ subjective experiences – rather than as a definite construct with a fixed definition. Consequently, we will make a distinction here between HRQoL and subjective QoL and indicate how Quality of Life was conceptualised in each study. When referring to both HRQoL and subjective QoL the term (HR)QoL is used.
We need to distinguish between two types of instruments developed to measure QoL – “generic” and “specific”. “Generic” measures (e.g. SF-36; WHOQoL) can be widely applied across populations and pathologies, allowing a comparison between different groups (Garrat et al., 2002, Vanagas et al., 2004); “specific” measures focus on a specific population, disease, function or problem (e.g. Lancashire QoL profile) (Guyatt et al., 1993, Vanagas et al., 2004). Another distinction can be made between “global” and “domain-specific” instruments (Wu & Yao, 2007). A “global” approach (e.g. satisfaction with life scale) assesses QoL in an overall manner (unidimensional), leading to one global score based on limited items. “Domain-specific” measures consider various life domains at the same time (e.g. subjective quality of life profile) and produce subscores for different domains (multidimensional). Therefore, researchers need to be aware of these conceptual and methodological issues and clarify what they mean (Dijkers, 2007) before choosing an instrument to measure QoL.
Despite a shift from objective to more subjective outcome measures in both general and mental health care, attention to consumers’ perspectives is still limited in the field of addiction research (Neale, Sheard, & Tompkins, 2007). Traditionally, evaluation studies start from a unilateral focus based on the norms and values of society, instead of listening to drug users’ own personal experiences (Fischer et al., 2001, Stajduhar et al., 2009). In general, attention is mostly given to socially desirable outcomes (e.g. no drug use, work, no criminal involvement) (Fischer et al., 2005, Mattick et al., 2003, Ward et al., 1999) and health-related outcomes (e.g. preventing infectious diseases) (Farrell et al., 2005, Verrando et al., 2005).
Until the 1990s, only limited attention was given to QoL in the addiction research field. This was in contrast to the large number of randomised controlled trials reporting on QoL research into other chronic illnesses, such as cancer and cardiovascular diseases (Sanders, Egger, Donovan, Tallon, & Frankel, 1998). One of the first studies of QoL among drug users by Ryan and White (1996) showed that the HRQoL of heroin users starting treatment was significantly worse than the general population and most comparable with individuals with psychiatric disorders. Torrens et al. (1997) observed a noticeable improvement of HRQoL among persons in methadone maintenance treatment (MMT), especially during the first month of treatment. A review of these early QoL studies (up to 2000) among alcohol and drug users (Rudolf & Watts, 2002) did not allow general conclusions due to the small number of studies and the use of different constructs (HRQoL and QoL) and instruments.
Since 2000, interest in QoL in addiction research – mainly among opiate users – has grown extensively. This goes hand in hand with the recognition that substance misuse is a chronic, relapsing disorder that may have negative consequences for various life domains (McLellan et al., 2000, Rudolf and Watts, 2002, Vanderplasschen et al., 2004). Relapse has been identified as a rule rather than an exception, especially among opiate-dependent persons (Van den Brink and Haasen, 2006, Van den Brink et al., 2003, Vanderplasschen et al., in press).
Despite the limitations mentioned above, QoL is an important indicator not captured by traditional and objective outcome measures and it can be used to tailor drug policy and treatment to drug users’ needs. Opiates remain the primary drug for the majority of those entering treatment (EMCDDA, 2008), and although the number of opiate-dependent individuals remains high (Kleber, 2005), only fragmented and often conflicting information on their QoL is available. A comprehensive review was needed to summarise the literature on QoL among opiate users and to set priorities for future QoL research.
Here the aim was to compare studies that have explored the (HR)QoL of opiate-dependent individuals and to assess the instruments used to measure (HR)QoL. First, we focused on studies that have compared opiate users’ (HR)QoL with the general population or other control group. Second, we assessed the influence of substitution treatment (e.g. methadone, buprenorphine) on (HR)QoL. Finally, the influence of potential mediators (e.g. gender, age, drug use, psychiatric comorbidity) on (HR)QoL was evaluated.
Section snippets
Methods
A comprehensive literature search was undertaken of databases such as ISI Web of Science, Pubmed/Medline, Cochrane Database of Systematic Reviews and Drugscope. The following terms were entered and combined as keywords: “addiction/substance (ab)use/drug (ab)use”, “quality of life/health-related quality of life/health status/satisfaction with life” and various opiate drugs such as “heroin”, “methadone” and “buprenorphine”. Reference lists of the retrieved articles and grey literature were
Conceptualisation and measurement of QoL
Instruments that measure QoL can be used for various purposes, such as comparing the QoL of subgroups or measuring changes in QoL (Guyatt et al., 1993). Most of the selected studies (n = 21) either used (HR)QoL as an outcome measure to compare the effectiveness of one type of substitution treatment among various subgroups of opiate-dependent persons or made the comparison between various substitution treatments (e.g. methadone, buprenorphine). Other studies (n = 11) have assessed the current
Opiate dependence and QoL
Based on this review of 38 articles, the subjective QoL and HRQoL of opiate-dependent individuals is relatively low as compared with the general population and people with various medical illnesses. One possible explanation may be that (HR)QoL is often assessed among opiate users starting treatment, which may result in an underestimation of (HR)QoL among the wider population of opiate users (Buchholz, Krol, Rist, Nieuwkerk, & Schippers, 2008). Moreover, drug users in treatment differ from
Conclusion
This review highlights the need for further research on QoL among drug users. It is often included in studies as a side issue, but research with a primary focus on QoL is limited and should be expanded to include a broad focus on all components of life that are related to the goodness of life. Starting from this perspective, it is recommended that a subjective, multidimensional QoL profile is applied rather than a one-dimensional approach. An increase in the uniformity of the instruments used
Conflict of interest
None.
Acknowledgement
We acknowledge funding from the Special Research Fund of Ghent University, Belgium.
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