Elsevier

Drug and Alcohol Dependence

Volume 148, 1 March 2015, Pages 195-202
Drug and Alcohol Dependence

Investigating the factor structure of the Illness Perception Questionnaire-Revised for substance dependence among injecting drug users in China

https://doi.org/10.1016/j.drugalcdep.2015.01.008Get rights and content

Highlights

  • Illness representations on substance dependence have strong implications on health outcomes and design for interventions.

  • The Illness Perception Questionnaire-Revised (IPQ-R) has been validated in various diseases but not in substance dependence.

  • The present study shows that the factor structure proposed by IPQ-R cannot be replicated among injection drug users (IDU).

  • Exploratory factor analysis of IPQ-R among IDU did not show an interpretable factor structure.

  • Use of the IPQ-R for substance dependence among IDU in China is cautioned until further validation.

Abstract

Background

The Illness Perception Questionnaire-Revised (IPQ-R) has commonly been used to measure illness representations of various diseases. The present study examined whether the original factor structure of the IPQ-R could be confirmed or a new structure could be established on substance dependence among injecting drug users (IDU) in China.

Methods

A total of 257 IDU completed the 38-item IPQ-R on substance dependence.

Results

Results of confirmatory factor analysis (CFA) showed that the 7-factor structure as proposed by the original IPQ-R reported poor goodness-of-fit statistics. Although removal of 12 items improved the model fit, the goodness-of-fit statistics were still below acceptable standards. Furthermore, factors obtained from the exploratory factor analysis (EFA) of the IPQ-R were not interpretable.

Conclusions

The CFA found that the original IPQ-R factor structure fit the data poorly. Factors derived from EFA were also not interpretable. Use of the IPQ-R for assessment of illness representations of substance dependence among IDU in China is cautioned until further validation.

Introduction

Drug use is a serious public health threat and a driving force of the HIV epidemics (Mathers et al., 2008). According to the China National Narcotics Control Commission, there were approximately 1.27 million registered heroin users in China in 2012 (China National Narcotics Control Commission, 2013). A systematic review estimated that there are 2.35 million injecting drug users (IDU) in China, which is the largest number in the world (Mathers et al., 2008). To design effective interventions, it is important to understand how IDU perceive issues related to substance dependence and how such perceptions affect behavioral and health outcomes. To achieve the purpose, conceptual models and measurement tools are both required.

Conceptually, there is a growing interest in understanding how people perceive various types of diseases, a concept known as illness representations. Illness representations include cognitive and emotional components, which are inter-related and influence coping and health outcomes jointly (Weinman and Petrie, 1997). According to Leventhal's Common Sense Model (CSM), individuals construct schematic representations of illness based on various idiosyncratic symptoms and illness episodes, and information obtained through social and cultural associations (Weinman and Petrie, 1997). The CSM specifies that illness representations have five dimensions: identity (identifying its symptoms), cause (attributing likely causes of the illness), timeline (considering whether the illness is acute or chronic), consequence (assessing the severity of the illness), and control (considering whether the illness is under volitional control). Meta-analysis shows that these dimensions are empirically distinct but are correlated with each other, while the strength of the correlations may differ according to specific disease conditions (Hagger and Orbell, 2003).

Regarding measurement tools, the Illness Perception Questionnaire (IPQ) (Weinman et al., 1996) was developed, based on the five aforementioned dimensions. The IPQ-Revised (IPQ-R) (Moss-morris et al., 2002) includes three additional constructs, namely the timeline-cyclical (considering whether the symptoms fluctuate over time), illness coherence (overall comprehensibility of the illness), and emotional representations (emotions that are evoked from the illness). Also, the original dimension of control was separated into two subscales: treatment control (beliefs about the treatability of the illness) and personal control (beliefs about personal ability in controlling the illness). The Chinese IPQ-R is available and has been validated among Chinese patients with hypertension (Chen et al., 2008) and Myocardial infarction (Song et al., 2007).

It is an important empirical question whether the factor structure proposed by the IPQ-R is applicable to a particular disease condition and a particular population. While relevant studies have reported that the factor structured proposed by the IPQ-R could be replicated in various conditions such as cancer (Giannousi et al., 2010), hypertension (Chen et al., 2008), depression (Cabassa et al., 2008), renal disease (Chilcot et al., 2012), cervical screening (Hagger and Orbell, 2005) and traumatic brain injury (Snell et al., 2010), its factor structure could not be confirmed on some conditions including musculoskeletal pain disorders and atopic dermatitis (Wittkowski et al., 2008, Nicholls et al., 2012). Other studies showed that the factor structure of IPQ-R could only be confirmed after removal and re-specification of some items (Brzoska et al., 2012). The authors of the IPQ and IPQ-R encouraged researchers to adapt their tools to study different disease conditions (Weinman et al., 1996, Moss-morris et al., 2002).

The importance of illness representations can be seen by their associations with health outcomes such as medication adherence (Horne and Weinman, 2002, Ross et al., 2004, Chen et al., 2011), self-care activities (Reynolds et al., 2009), psychological distress and depression (Broadbent et al., 2011, Scollan-Koliopoulos et al., 2011, Dempster et al., 2012, Paddison et al., 2010, Paschalides et al., 2004, Knibb and Horton, 2008) across conditions such as hypertension (Chen et al., 2011, Ross et al., 2004), cancer (Dempster et al., 2012), allergy (Knibb and Horton, 2008), diabetes (Mc Sharry et al., 2011, Paddison et al., 2010), and HIV (Reynolds et al., 2009). Such associations have also been investigated among healthy individuals (Mo and Lau, 2014, Figueiras and Alves, 2007). Importantly, illness representations can be used as a means of health promotion as they are modifiable (Weinman and Petrie, 1997). It is potentially important to understand illness representations on substance dependence, which is a chronic and often relapsing disease that causes compulsive substance seeking and use, despite harmful consequences to the individuals (National Institute on Drug Abuse, 2012). Illness representations on substance dependence have strong implications on health outcomes and interventions among IDU. It is an important but totally unexplored concept.

Substance dependence is a disease as well as a behavior. According to the Fourth Edition and Text Revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) published in 2000, substance dependence is based on presence of three or more of seven criteria (such as tolerance, withdrawal symptoms, use of a substance in a larger amount) during a 12-month period (American Psychiatric Association, 2000). In the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) published in 2013, the term substance use disorder was used. Classification of substance use disorder is based on eleven criteria (such as craving, tolerance, withdrawal symptoms), in which a minimum of two to three criteria is required for mild substance use disorder diagnosis, while four to five is moderate and six to seven is severe (American Psychiatric Association, 2013). At the time of the study, DSM-5 was not issued; the study was hence guided by DSM-IV-TR.

It is understood that some IDU may not be classified as substance dependence according to DSM-IV-TR, although they may be at high risk of substance dependence. It is important to understand illness representations of substance dependence among IDU as such perceptions are potentially related to their high risk behaviors, service utilization and mental health. Previous studies on illness representations among people who are potentially but not yet suffering from a disease are meaningful and have been conducted (Mo and Lau, 2014, Figueiras and Alves, 2007). Drug use is illegal in China and offenders are arrested and sent to compulsory detoxification institutions, where personal freedom is deprived for retention of 3 to 6 months. Repeat offenders are sentenced to a re-education through labor (RTL) center for 1 to 3 years (Cohen and Amon, 2008). As drug use may be considered as a bad habit, personality flaw, or moral weakness instead of a medical disorder which needs medical intervention in China (Tang and Hao, 2007), there are reasons to suspect that the factor structure of the IPQ-R for substance dependence may be different from that of the original structure of the IPQ-R.

As the first step to utilize the concept of illness representations on substance dependence, we need to possess a validated measurement tool. We investigated whether the factor structure of the IPQ-R on substance dependence can be confirmed by confirmatory factor analysis (CFA), or established by exploratory factor analysis (EFA) in a population of IDU in China.

Section snippets

Study population and sampling

The study was conducted in Dazhou, Sichuan province, China, which has a total population of 6.5 million and more than 5000 registered drug users according to official data (Gu et al., 2008c). One study has shown that 74.4% of the drug users in Sichuan injected drugs and 98.2% of whom used heroin (Liu et al., 2006). Inclusion criteria were: (1) aged 18 or above, (2) having heroin as the major mode of drug use, and (3) having injected heroin at least once in the last six months.

As there is no

Characteristics of the participants

Of the 257 participants, 57.6% were male and 37.3% were <35 years old (mean = 36.37, SD = 6.94, range = 19–53). More than two-third (71.6%) of them had attained lower than junior high school level of education and nearly one-third (31.5%) were divorced. About one-third (33.1%) of them reported no monthly personal income. Nearly half of the participants (47.1%) reported drug use on a daily basis. Respectively, 75.1% and 51.0% reported that they have attended compulsory drug rehabilitation and RTL.

Discussion

In the present study, the proposed factor structure of the IPQ-R on substance dependence was not confirmed by CFA. Furthermore, the EFA did not show any interpretable data structure. The findings are not exceptional as a number of previous studies could not confirm the factor structure of the IPQ-R (Wittkowski et al., 2008, Nicholls et al., 2012) or could only confirm the factor structure after several modifications (Brzoska et al., 2012), reminding us that the IPQ-R may not be fully applicable

Role of funding source

Nothing declared

Conflict of interest

All authors declare they have no conflict of interest

Contributors

PM, JTFL, JG, JL involved in the conception and design of the work; JG involved in the acquisition of data; PM, KC involved in the analysis of data; all authors interpreted the data; PM, JTFL wrote the manuscript, all authors revised the manuscript critically for important intellectual content and provided final approval of the version to be published.

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