How effective is drug testing as a workplace safety strategy? A systematic review of the evidence

Accident Analysis and Prevention 71 (2014) 154–165

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How effective is drug testing as a workplace safety strategy? A systematic review of the evidence Ken Pidd ∗ , Ann M. Roche 1 National Centre for Education and Training on Addiction, Flinders University, GPO Box 2001, Adelaide, SA, 5001, Australia

a r t i c l e

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Article history: Received 7 November 2013 Received in revised form 4 April 2014 Accepted 20 May 2014 Keywords: Workplace Drug testing Safety Evaluation Systematic review

a b s t r a c t The growing prevalence of workplace drug testing and the narrow scope of previous reviews of the evidence base necessitate a comprehensive review of research concerning the efficacy of drug testing as a workplace strategy. A systematic qualitative review of relevant research published between January 1990 and January 2013 was undertaken. Inclusion criteria were studies that evaluated the effectiveness of drug testing in deterring employee drug use or reducing workplace accident or injury rates. Methodological adequacy was assessed using a published assessment tool specifically designed to assess the quality of intervention studies. A total of 23 studies were reviewed and assessed, six of which reported on the effectiveness of testing in reducing employee drug use and 17 which reported on occupational accident or injury rates. No studies involved randomised control trials. Only one study was assessed as demonstrating strong methodological rigour. That study found random alcohol testing reduced fatal accidents in the transport industry. The majority of studies reviewed contained methodological weaknesses including; inappropriate study design, limited sample representativeness, the use of ecological data to evaluate individual behaviour change and failure to adequately control for potentially confounding variables. This latter finding is consistent with previous reviews and indicates the evidence base for the effectiveness of testing in improving workplace safety is at best tenuous. Better dissemination of the current evidence in relation to workplace drug testing is required to support evidence-informed policy and practice. There is also a pressing need for more methodologically rigorous research to evaluate the efficacy and utility of drug testing. © 2014 Elsevier Ltd. All rights reserved.

1. Introduction There has been global growth in the use of workplace drug testing as a response to drug related risk to safety and productivity (George, 2005; Verstraete and Pierce, 2001; Walsh, 2008). The proportion of American Management Association member companies that utilised workplace drug testing grew overall from 21% in 1987 to 62% in 2004, despite a 19% decline since the mid 1990s (Frone, 2013). By 2004, nearly half the US workforce (48.8%) reported that their workplace utilised some form of drug testing (Larson et al., 2007). While data on the prevalence of workplace drug testing in other countries is scarce (Pierce, 2007), the relatively recent introduction of workplace drug testing legislation in Australia, Finland,

∗ Corresponding author. Tel.: +61 8 82017535; fax: +61 8 82017550. E-mail addresses: ken.pidd@flinders.edu.au (K. Pidd), ann.roche@flinders.edu.au (A.M. Roche). 1 Tel.: +61 8 82017575; fax: +61 8 82017550. http://dx.doi.org/10.1016/j.aap.2014.05.012 0001-4575/© 2014 Elsevier Ltd. All rights reserved.

Ireland and Norway provides evidence of increasing support for workplace testing (CASR, 1998; Pierce, 2012). The main aim of drug testing is to improve workplace safety and productivity. In the US, the focus is on creating a ‘drug free’ workplace by deterring employee drug use (Frone, 2013; MacDonald et al., 1993). The underpinning rationale is that drug testing can identify drug using employees or job applicants and these individuals can be dismissed or refused employment, thus providing a deterrent effect. In contrast, the focus in UK, Canadian, and Australian workplaces is to improve safety and productivity by reducing the incidence or risk of alcohol or drug related injuries and accidents (Independent Enquiry into Drug Testing at Work, 2004; Keay et al., 2010; Walker and Sack, 2003). The rationale underpinning this aim is that drug testing can detect employees whose performance may be impaired as a result of their drug use and thereby any risk to safety can be reduced or eliminated by removing these employees, either temporarily or permanently, from the workplace. Despite the substantial growth in drug testing as a workplace strategy and the apparent logic of the underlying rationale, the

K. Pidd, A.M. Roche / Accident Analysis and Prevention 71 (2014) 154–165

Arcles idenfied through database searching (n = 508)

155

Addional arcles idenfied through arcle reference lists (n = 4)

Total arcles aer duplicates removed (n =359)

Total arcles excluded (n = 74) • Primary focus not workplace tesng (n = 62) • Focus on tesng for occupaonal exposure to chemicals (n = 12)

Assessed arcles classified by type of publicaon (n = 285)

Legal/ethical (n = 31)

Policy/procedure (n =35)

Measurement (n = 42)

Evaluaon (n = 27)

Included = 23

Reviews (n = 17)

Descripve (n = 133)

Excluded = 4

Fig. 1. Flow chart of search and exclusion process.

evidence for the efficacy of testing to deter employee drug use or improve workplace safety appears inconclusive. Early reviews found a paucity of quality research and concluded few definitive conclusions could be drawn regarding the efficacy of workplace drug testing (Kraus, 2001; Macdonald and Wells, 1994; Normand et al., 1994). However, these reviews largely examined studies undertaken 15–20 years ago. The three most recent reviews of evidence concerning the efficacy of testing also found there was insufficient quality evidence to conclude that drug testing could deter use or prevent occupational injuries (Cashman et al., 2009; Frone, 2013; Macdonald et al., 2010). Cashman et al. (2009) undertook a quantitative systematic Cochrane review of studies that examined the effectiveness of drug testing in preventing workplace injuries among road transport drivers. However, this review was restricted to a single industry and occupation and the findings may not generalise to other industries or occupations. Similarly, Macdonald et al. (2010) focused on one drug testing technology (urinalysis) to detect a single type of drug (cannabis). Employees widely use cannabis, and urinalysis is a testing technology routinely used in the workplace. However, other illicit drugs are also relatively prevalent in US (Frone, 2006), European (Verstraete and Pierce, 2001) and Australian (Pidd et al., 2011) workforces and other types of testing technologies, such as saliva analysis, are increasingly common (Walsh, 2008). While the most recent review (Frone, 2013) is more comprehensive and broader in scope, it largely summarised the extent and limitations of the current evidence base without providing a systematic description of the methodology, outcomes and quality of individual studies.

Of the more recent reviews, only one (Cashman et al., 2009) adopted a systematic approach to the selection and inclusion criteria and the methodological evaluation of studies reviewed. However, this review was restricted to one industry and occupation. While qualitative reviews that do not adopt an explicit systematic approach are informative and useful, a systematic approach is essential for evidence based policy and practice as it is more likely to identify any methodological limitations in the existing evidence and produce more reliable and less biased conclusions. To complement and extend the previous reviews undertaken, a systematic qualitative literature review was carried out to appraise the effectiveness of workplace drug testing as a policy strategy to improve workplace safety and deter drug use and to provide a comprehensive overview of the current state of knowledge in this area.

2. Method A systematic literature search was undertaken to locate and review research concerning the effectiveness of workplace drug testing. The review was designed to answer the following questions: • Does workplace drug testing reduce occupational accident or injury rates? • Does workplace drug testing deter employee drug use?

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2.1. Search strategy

3. Results

The CINAHL, Medline, PsycLit, ProQuest and Web of Knowledge citation databases were searched for relevant research articles published between January 1990 and January 2013 using combinations of the following terms:

Of the 23 primary studies included in the review, six examined the efficacy of testing in deterring drug use (see Tables 1 and 2) and 17 examined the efficacy of testing in reducing occupational injury rates (see Tables 3 and 4). All studies were undertaken in the USA.

Work* Occupation* Reduc* Deter*

Alcohol Employ* Impair* Death

Drug Test* Injur* Fatal*

Substance Screen* Detect* Industry

A total of 508 articles were identified (Fig. 1). Of these, 153 duplicates were removed and an additional four papers included after an examination of reference lists provided in the assessed articles. A further 74 articles were removed as they did not focus on workplace testing (n = 62), or involved testing for occupational exposure to chemicals (n = 12). The remaining 285 articles were classified according to the main focus of each article. The majority (n = 133) were either descriptions of testing programs, analyses of psychological and sociological aspects of testing, or commentaries. Thirty one concerned ethical or legal issues, 35 policy and procedural issues, and 42 measurement and technical issues. Seventeen were literature reviews, of which six focused on evaluations of workplace testing. Of the remaining 27 evaluation articles, seven reported studies that examined the effectiveness of workplace testing in deterring drug use and 20 reported studies that examined the effectiveness of workplace testing in reducing workplace accidents or injuries. One article that examined the deterrent effect of testing (Mehay and Pacula, 1999) was excluded as it focused on a military population and as such may not be generalizable to the civilian workforce. In addition, three articles that examined preemployment screening (Normand et al., 1990; Ryan et al., 1992; Zwerling et al., 1990) were excluded as they examined the relationship between a positive pre-employment testing and subsequent work outcomes, rather than the effectiveness of testing in reducing workplace accidents or injuries per se. This resulted in a total of 23 included articles. The methodological rigour and adequacy of these studies were evaluated against a modified version of the Effective Public Health Practice Project (EPHPP) qualitative assessment tool for quantitative studies (Effective Public Health Practice Project, 1998). The tool was developed to assess the methodological quality of primary studies in public health (Thomas et al., 2004) and is based on guidelines set out by Mulrow et al. (1997) and Jadad et al. (1996). Guidelines provided in the EPHPP tool dictionary were used to assess the methodological adequacy of each study against four criteria (selection bias, study design, confounders, and data collection) as either strong, moderate, or weak. Information concerning two other criteria (analysis and intervention integrity) was summarised (Tables 2 and 4). As the review identified no randomised controlled trial studies, and most were cross-sectional and/or examined aggregated data, two EPHPP assessment criteria (blinding and withdrawal/dropouts) were not included. Based on the four assessment criteria utilised, each study was given an overall methodological adequacy rating consistent with EPHPP tool instructions. Studies that obtained at least two ratings of strong with no ratings of weak for any of the assessment criteria were assessed as methodologically strong. Studies that obtained less than two strong ratings but no more than one weak rating for any of the assessment criteria were assessed as methodologically moderate. Studies that obtained two or more weak ratings for any of the assessment criteria were assessed as methodologically weak. Two reviewers independently undertook the methodological assessment. For the majority of studies assessed (>85%) the reviewers’ ratings were consistent. Differences in assessment ratings were resolved by discussion.

3.1. Studies examining deterrent effects All six of the deterrence studies indicated that workplace drug testing was associated with lower levels of employee drug use. One study utilised a pre/post cohort design to examine preemployment screening among a sample (N = 987) of hospital job applicants with drug test results as the outcome variable (Lange et al., 1994). The remaining five deterrence studies involved crosssectional surveys of large representative samples of the national workforce (Carpenter, 2007; French et al., 2004; Hoffmann and Larison, 1999; Larson et al., 2007; Zhang et al., 1999). All five of these cross-sectional studies utilised data collected via the same annual national survey of alcohol and drug use that was conducted over different years. However, while utilising the same data source, these cross-sectional studies varied in the type of testing program examined. Two examined pre-employment and random testing (Hoffmann and Larison, 1999; Larson et al., 2007), two examined pre-employment, random, post-accident, and for cause testing (Carpenter, 2007; Zhang et al., 1999), one examined preemployment, random and for cause testing (French et al., 2004). Only two studies distinguished between alcohol and illicit drug testing (Larson et al., 2007; Zhang et al., 1999). The five cross-sectional studies also varied in the self-report measures utilised. Two studies used a composite measure of any illicit drug use or non-medical use of pharmaceuticals in the past month and a measure of past month heavy alcohol use, defined as five or more drinks on five or more occasions (Larson et al., 2007; Zhang et al., 1999). French et al. (2004) used a composite measure of any illicit drug use in the past year and current illicit drug use, defined as using one or more illicit drugs at least once a week. Hoffmann and Larison (1999) used a measure of cocaine and cannabis use in the previous 3 or more years, the previous 1–3 years, and number of days used in the past year (1–2, 3–51 times, 51 or more). The methodological rigour of the six deterrence studies is described in Table 2. All six deterrence studies were assessed as methodologically weak. Five were cross-sectional studies that measured drug use at one point in time. Such designs are inappropriate for examinations of causal relationships. While Lange et al. (1994) utilised a more rigorous pre/post-test design, the use of a nonrandom convenience sample, the lack of a control group, and the use of organisational level data to draw inferences about individual behaviour change are major limitations. 3.2. Studies examining the effectiveness of testing in reducing accident/injury rates Of the 17 studies that examined the effectiveness of testing to reduce workplace accident or injury rates (Table 3), 11 reported that drug testing was associated with a reduction in accidents (Brady et al., 2009; Gerber and Yacoubian, 2001; Jacobson, 2003; Miller et al., 2007; Minchin et al., 2006; Morantz and Mas, 2008; Ozminkowski et al., 2003; Schofield et al., 2013; Snowden et al., 2007; Spicer and Miller, 2005; Swena and Gaines, 1999), three reported no association (Dell and Berkhout, 1998; Kesselring and Pittman, 2002; Kitterlin and Moreo, 2012), and three reported mixed results (Feinauer and Havlovic, 1993; Lockwood et al., 2000; Wickizer et al., 2004). These studies varied by study design, the

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Table 1 Summary of studies examining testing deterrent effect (from 1990 to Jan 2013). Study

Participants and setting

Test type

Design

Measures

Outcome

Lange et al. (1994) USA

987 hospital job applicants (21% male; 77% <35 yrs old)

Pre-employment

Pre/post

Hoffmann and Larison (1999) USA

9097 employed respondents to 1994 NHSDA (54% male; Mage = 39 yrs)

Pre-employment and random

Cross-sectional

Urine test results T1 (1989) and T2 (1991) Frequency of cannabis and cocaine use (self-report)

Zhang et al. (1999) USA

15,012 employed respondents (aged 18–49 yrs) to the 1994 (58.9% male) and 1997 NHSDA (59.5% male)

Pre-employment random, for cause and post-accident (alcohol and drug)

Cross-sectional

Past month any drug use (self-report) Past month heavy alcohol use (self-report)

French et al. (2004) USA

15,400 employed respondents to the 1997 and 1998 NHSDA (46.5% male; Mage = 36.4 yrs)

Pre-employment for cause and random

Cross-sectional

Past week any drug use (self-report) Past year any drug use (self-report)

Carpenter (2007) USA

57,397 employed 2000 and 2001 NHSDA and 2002 NSDUH respondents (58% male; 40% <35 yrs old)

Pre-employment random, for cause and post-accident

Cross-sectional

Past month cannabis use (self-report)

Larson et al. (2007) USA

73,325 employed 2002, 2003, and 2004 NSDUH respondents (gender % and Mage not reported)

Pre-employment and random (alcohol and drug)

Cross-sectional

Past month any drug use (self-report) Past month heavy alcohol use (self-report)

Positive test rate declined significantly from 10.8% (T1) to 5.8% (T2) Frequent drug use significantly less likely among employees of companies that test than employees of companies that do not test Compared to 1994 survey respondents employed in non-testing companies, drug use was significantly less likely for 1994 survey respondents employed in companies that conducted random or pre-employment tests. No significant differences in heavy alcohol use by drug testing status were observed No significant difference in drug use or heavy alcohol use by employer testing status was observed for 1997 survey respondents Past year and past week drug use was significantly less likely for employees of companies with random, for-cause or pre-employment drug testing compared to employees of companies that did not test Cannabis use significantly less likely among employees of testing companies, compared to employees of non-testing companies A similar significant effect was observed for employees of companies that did not test but provided either drug education, a written policy, or an EAP Past month drug use significantly less for employees of testing companies compared to employees of non-testing companies No significant difference in past month heavy alcohol use between employees of testing and non-testing companies

NHSDA = US National Household Survey on Drug Abuse; NSDUH = US National Survey on Drug Use and Health. The NHSDA and the NSDUH are the same annual survey. In 2002 the name of the National Household Survey on Drug Abuse was changed to the National Survey on Drug Use and Health.

type of testing program examined, outcome measures, and methodological rigour. Study designs included time series, cross-sectional, pre/post, and matched pairs. Seven studies utilised a time series design involving 610 metal foundry employees (Dell and Berkhout, 1998), 219 hotel employees (Lockwood et al., 2000), 1791 manufacturing employees (Ozminkowski et al., 2003), 256 state based companies (Wickizer et al., 2004), employees of five transport companies (Spicer and Miller, 2005), 26,000 rail transport company

employees (Miller et al., 2007), and the national truck driving workforce (Swena and Gaines, 1999; Snowden et al., 2007). Six studies were cross-sectional surveys of 69 (Gerber and Yacoubian, 2001) and 34 (Minchin et al., 2006) construction company representatives, 110 restaurant management representatives (Kitterlin and Moreo, 2012), a representative sample of the national workforce (Kesselring and Pittman, 2002), the national commercial truck driving workforce (Jacobson, 2003) and one was a cross-sectional analysis of workers’ compensation data for 1360 construction

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Table 2 Summary of the methodological rigour of studies examining testing deterrent effect (from 1990 to Jan 2013). Study

Control for selection bias

Study design

Control for confounding

Data collection

Analysis

Intervention integrity

Overall rating

Lange et al. (1994)

Weak

Moderate

Weak

Moderate

Post-intervention sample not the same as pre-intervention sample

Weak

Hoffmann and Larison (1999)

Strong

Weak

Weak

Moderate

No sample size calculation Unit of analysis: organisation Unit of analysis: individual

Weak

Zhang et al. (1999)

Strong

Weak

Weak

Moderate

Unit of analysis: individual

French et al. (2004)

Strong

Weak

Weak

Moderate

Unit of analysis: individual

Carpenter (2007)

Strong

Weak

Weak

Moderate

Unit of analysis: individual

Larson et al. (2007)

Strong

Weak

Weak

Moderate

Unit of analysis: individual

Types of testing programs varied among survey respondents Frequency of testing and proportion of employees tested not reported Types of testing programs varied among survey respondents Frequency of testing and proportion of employees tested not reported Types of testing programs varied among survey respondents Frequency of testing and proportion of employees tested not reported Types of testing programs varied among survey respondents Frequency of testing and proportion of employees tested not reported Types of testing programs varied among survey respondents Frequency of testing and proportion of employees tested not reported

companies (Schofield et al., 2013). Two studies were pre/post designs with employees of a large retail chain (Morantz and Mas, 2008) and 48 manufacturing and service industry workplaces (Feinauer and Havlovic, 1993). One study utilised a matched pairs design that examined the national trucking industry workforce (Brady et al., 2009). Four studies examined pre-employment, random, for cause, and post-accident testing (Jacobson, 2003; Minchin et al., 2006; Ozminkowski et al., 2003; Schofield et al., 2013). Five studies examined random testing, two of which examined random alcohol and random drug testing (Miller et al., 2007; Spicer and Miller, 2005), while two examined only random alcohol testing (Brady et al., 2009; Snowden et al., 2007) and one examined only random drug testing (Swena and Gaines, 1999). Two studies examined pre-employment testing (Dell and Berkhout, 1998; Kitterlin and Moreo, 2012). One study examined pre-employment and random testing (Lockwood et al., 2000), one examined pre-employment and for cause testing (Feinauer and Havlovic, 1993) and one examined post-accident testing (Morantz and Mas, 2008). The remaining three studies did not report the type of testing examined (Gerber and Yacoubian, 2001; Kesselring and Pittman, 2002; Wickizer et al., 2004). Outcome measures of four studies were national road accident fatality rates among trucking industry employees (Brady et al., 2009; Jacobson, 2003; Snowden et al., 2007; Swena and Gaines, 1999). The outcome measures in the remaining 13 studies were all indicators of workplace fatal and non-fatal accident/injury rates. Two of these studies relied on self-report data (Kitterlin and Moreo, 2012; Minchin et al., 2006), while 11 accessed reportable injury data records. Of these 11 studies, one measured accident/injury rates at a state level (Kesselring and Pittman, 2002), one at a geographical district level involving more than one workplace from the

Weak

Weak

Weak

Weak

same organisation (Morantz and Mas, 2008), one at the organisational and national level (Miller et al., 2007), while the remaining studies measured injury rates at the organisational level. In terms of methodological rigour, eight studies (47.1%) were assessed as methodologically weak, eight were assessed as demonstrating moderate methodological rigour, and one was assessed and methodologically strong. Five of the methodologically weak studies measured injury rates at a single point in time using a cross-sectional survey (Gerber and Yacoubian, 2001; Kesselring and Pittman, 2002; Kitterlin and Moreo, 2012; Minchin et al., 2006; Schofield et al., 2013); a design that is inappropriate for examinations of causal relationships. The other three studies adopted more rigorous designs, but were flawed by potential selection bias and failure to control for confounding variables (Dell and Berkhout, 1998; Feinauer and Havlovic, 1993; Lockwood et al., 2000). Five of the eight studies that were assessed as demonstrating moderate methodological adequacy found random alcohol and drug (Miller et al., 2007; Spicer and Miller, 2005), random drug (Swena and Gaines, 1999; Jacobson, 2003), random alcohol (Snowden et al., 2007), and post-accident (Morantz and Mas, 2008) testing programs were associated with reductions in injury rates. Of the remaining two studies one that failed to report the type testing program (Wickizer et al., 2004) also found testing was associated with a reduction in injury rates, while one that examined a comprehensive testing program (Ozminkowski et al., 2003) reported a non-significant reduction in injury rates. However, the methodological rigour of these seven studies was limited by the failure to adequately account for potential confounding variables that may have influenced any observed effect. Only one study was assessed as demonstrating strong methodological rigour. Brady et al. (2009) adopted a quasi-experimental design that compared the prevalence of alcohol involvement in

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Table 3 Summary of studies evaluating the effectiveness of testing in reducing workplace accidents/injuries (from 1990 to Jan 2013). Study

Participants and setting

Test type

Design

Measures

Outcome

Feinauer and Havlovic (1993) USA

48 Wisconsin manufacturing and service industry companies (employee sample size, gender and age not reported)

Preemployment post-accident and for cause

Crosssectional/time series

Aggregated accident rate (5 years period)

Dell and Berkhout (1998) USA

610 metal foundry employees (gender and age not reported) Interstate commercial truck drivers (sample size, gender and age not reported) 219 employees of three Florida hotels (gender and age not reported)

Preemployment

Interrupted time series

Random

Interrupted time series

Preemployment and random

Interrupted time series

Monthly accident data (1980–1994) Fatality rate per 100 mile travelled (1988–1990) Monthly accident rate (1992–1996)

No significant difference in accident rates between 12 testing and 36 non-testing companies Pooled time series regression analysis of injury data for the 12 testing companies indicated post-accident testing was associated with a significant reduction in accident rates Introduction of testing not significantly associated with a reduction in monthly accident rate A significant reduction in road fatality rates was observed for 2 years post testing implementation

Management representatives of 69 construction companies (employee sample size, gender and age not reported) National workforce (gender and age not reported)

Not reported

Cross-sectional

Occupational accident/illness incident rate MODa rating

Not reported

Cross-sectional

Occupational accident/illness incident rate

Preemployment for cause, post-accident, random Preemployment for cause, post-accident, random Not reported

Crosssectional/time series

Aggregated state fatal truck accident rate (1983–1998)

Interrupted time series

Monthly injury rate (1996–1999)

Drug testing rate associated with a non-significant (p = .053) reduction in injury rates

Pre/post with comparison group

Injury incidence rates (1994–2000)

Drug free program associated with significant reduction in reported injury rates for three of nine industries examined (construction, manufacturing and services) and in lost time (>4 days) injury rates for two industries (construction and services) Industry wide implementation of both random drug and alcohol testing was associated with a significant decline in injury risk A peer intervention program (Peer Care) introduced into one of the five companies was also associated with a significant decline in injury risk prior to the introduction of random drug or alcohol testing Survey respondents employed in 29 companies that tested reported a 10–60% reduction in accident rates post testing implementation

Swena and Gaines (1999)

Lockwood et al. (2000) USA

Gerber and Yacoubian (2001) USA

Kesselring and Pittman (2002) USA

Jacobson (2003) USA

National commercial truck driving workforce (gender and age not reported)

Ozminkowski et al. (2003) USA

1791 manufacturing company employees (gender and age not reported)

Wickizer et al. (2004) USA

256 Washington State companies (employee sample size, gender and age not reported)

Spicer and Miller (2005) USAb

Approx. 125,000 employees of five transport industry companies (gender and age not reported)

Random alcohol and drug

Interrupted time series

Monthly injury rate (1983–1996)

Minchin et al. (2006) USA

34 Florida based construction companies (gender and age not reported)

Cross-sectional

Accident rates (self-report by company representatives)

Miller et al. (2007) USAb

26,000 employees of a rail transport company (gender and age not reported)

Preemployment for cause, post-accident, and random Random alcohol and drug

Interrupted time series with comparison group

Monthly injury rate (1983–1999)

No significant reduction in accident rates for the two hotels that introduced pre-employment testing, but a significant reduction in accident rates was observed for the one hotel that introduced both random and pre-employment testing Comparison of drug testing and non-drug testing companies indicated drug testing was associated with a significantly lower occupational accident/illness rates and a significantly lower MOD rating No significant difference in occupational accident/illness rates between states according to state based workplace drug testing legislation category (restrictive, supportive, neutral, or none) A significant reduction in road fatality rates (9–10%) was associated with the introduction of testing

The combination of a peer-based program (Peer Care) and drug testing was associated with an approximate one-third reduction in injury rates. Alcohol testing and related Peer Care enhancements were associated with a further 17% reduction in injuries

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Table 3 (Continued) Study

Participants and setting

Test type

Design

Measures

Outcome

Snowden et al. (2007) USA

National heavy truck driving workforce (aged 21–65 yrs, sample size and gender not reported)

Random alcohol

Interrupted time series with comparison group

Pooled fatal road accident data (1988–2003)

Morantz and Mas (2008) USA

Retail chain employees (sample size, age and gender not reported)

Post-accident

Pre/post with comparison group

Brady et al. (2009) USA

69,295 motor carrier drivers and 83,436 non-motor-carrier drivers (82.5% male, age not reported)

Random alcohol

Matched pairs

Operational district levelc accident/injury rate (2002–2007) Aggregated national road accident fatality data (1982–2006)

Compared to passenger car drivers, heavy truck drivers were less likely to be involved in fatal accidents after the introduction of alcohol testing Introduction of mandatory alcohol testing for heavy truck drivers associated with a significant reduction (14.5%) in alcohol related fatalities Post-accident testing was associated with a significant decline (12–18%) in accident rates

Kitterlin and Moreo (2012) USA

110 managers, supervisors and HR personnel employed in Las Vegas restaurants (age and gender not reported) 1360 construction companies (employee sample size, gender and age not reported)

Preemployment

Cross-sectional

Self-report accident rates

Preemployment for cause, post-accident, and random

Cross-sectional

Aggregated workers’ compensation data (2004–2009)

Schofield et al. (2013) USA

Introduction of mandatory alcohol testing for commercial drivers was associated with a significant reduction (23%) in alcohol involvement in fatal crashes by motor carrier drivers No significant difference in accident rates between restaurants with or without a pre-employment testing program

Compared to non-testing companies, those with testing programs had slightly lower (non-significant) injury rates

a An MOD (compensation experience-rating modification factor) is a comparison of a company’s annual losses in insurance claims against its policy premiums over a 3-year period. As MOD increases, so does workers’ compensation insurance premiums. b While the Spicer and Miller (2005) and the Miller et al. (2007) studies evaluated the same company program, differences in sample size, data collection time frames, outcome variables and methodology warrant inclusion as separate studies. c Each operational district level consists of up to 15 workplaces, belonging to the retail chain, that operate in distinct geographical districts.

fatal crashes for 13 years (1982–1994) prior to the implementation of mandatory alcohol testing for heavy truck drivers and the prevalence rate for 12 years (1995–2006) post implementation. Prevalence rates for heavy truck drivers were compared with prevalence rates for other drivers matched on tempo-spatial variables such as the date, time, location, geographic region, US state, road and weather conditions. Such a study design substantially reduces the effect of confounding factors. 4. Discussion This paper presents one of the most comprehensive and systematic qualitative reviews of evidence concerning the effectiveness of workplace drug testing as a workplace safety strategy undertaken to-date. The only two previous reviews that have adopted a systematic approach to selection and inclusion criteria and the methodological evaluation of studies reviewed are either dated (Kraus, 2001), or restricted to one industry and occupation (Cashman et al., 2009). The current review included studies that examined a wider range of industry and occupational settings. Many of these studies are often cited as evidence supporting the efficacy of workplace testing. However the current review found the overall quality of most of these studies weak, indicating that a poor evidence base has been relied upon to guide the adoption of testing as a workplace strategy. Given the growth in the prevalence of workplace testing over the past few decades, the findings of this review are important to ensure the development of evidence based workplace safety programs. Of the 285 published papers identified by this review, only 23 (8.1%) reported studies that evaluated the effectiveness of testing in deterring employee drug use or reducing occupational injury or accident rates. Of these 23 studies, the majority (60.9%) were

assessed as methodologically weak and only one demonstrated strong methodological rigour. The review found no randomised controlled trials, and other study designs utilised generally suffered from serious methodological limitations including; lack of randomisation and/or inclusion of matched comparison groups, low response rates and/or small sample sizes, failure to control for potentially confounding variables, and the use of aggregate or ecological data to examine the effect of testing on individual behaviour. Also, many studies that reported a significant effect failed to report the effect size, making it difficult to determine if the observed results were of practical importance. Moreover, where an effect size was provided it was often in relative rather than absolute terms. Providing estimates of relative risk without information concerning absolute risk may lead to overestimation of the extent of the change. For example, Snowden et al. (2007) reported that the introduction of random alcohol testing resulted in heavy truck drivers being 14.5% less likely to be involved in an alcohol related fatal accident. However the proportion of alcohol involved fatal heavy truck accidents in the pre-testing study period (1988–1993) declined from 4.4% to 2.7% in the post testing study period (1994–2003), a reduction of 1.7% in absolute terms. Thus, while the current review differs from previous reviews in terms of the approach and the larger number and wider scope of studies examined, it reaches a similar conclusion in finding that much of the evidence concerning the efficacy of workplace testing is of poor quality (Cashman et al., 2009; Frone, 2013; Kraus, 2001; Macdonald et al., 2010; Macdonald and Wells, 1994; Normand et al., 1994). Such a consistent finding has important implications for the credibility of the evidence concerning the efficacy of drug testing as a workplace strategy. In particular, the evidence base for the effectiveness of testing in deterring employee drug use or improving

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Table 4 Summary of methodological adequacy of studies evaluating the effectiveness of testing in reducing workplace injuries/accidents (from 1990 to Jan 2013). Study

Control for selection bias

Study design

Control for confounding

Data collection

Analysis

Intervention integrity

Overall rating

Feinauer and Havlovic (1993)

Weak

Moderate

Weak

Moderate

No sample size calculation Unit of analysis: organisation

Weak

Dell and Berkhout (1998)

Weak

Moderate

Weak

Moderate

No sample size calculation Unit of analysis: organisation

Swena and Gaines (1999)

Strong

Moderate

Weak

Moderate

Lockwood et al. (2000)

Weak

Moderate

Weak

Weak

Unit of analysis: aggregated national fatality data No sample size calculation Unit of analysis: organisation

Gerber and Yacoubian (2001)

Weak

Weak

Weak

Moderate

Types of testing programs varied between different testing companies included in the study Frequency of testing and proportion of employees tested not reported Pre-employment screening began late in the study Proportion of incumbent employees exposed to pre-employment testing not reported Random testing conducted according to mandated and regulated DOTa guidelines Frequency of testing and proportion of employees tested not reported Intervention potentially compromised by high turnover rate (average of 328% per hotel during study period) Types of testing programs examined not reported Frequency/coverage of testing across companies not reported

Kesselring and Pittman (2002)

Moderate

Weak

Weak

Moderate

Jacobson (2003)

Strong

Moderate

Weak

Moderate

Ozminkowski et al. (2003)

Weak

Moderate

Moderate

Moderate

Wickizer et al. (2004)

Moderate

Moderate

Weak

Moderate

Spicer and Miller (2005)

Moderate

Moderate

Weak

Moderate

Minchin et al. (2006)

Weak

Weak

Weak

Weak

Miller et al. (2007)

Moderate

Moderate

Weak

Moderate

Snowden et al. (2007)

Strong

Moderate

Moderate

Moderate

Morantz and Mas (2008)

Moderate

Moderate

Moderate

Moderate

Brady et al. (2009)

Strong

Strong

Strong

Moderate

Kitterlin and Moreo (2012)

Weak

Weak

Weak

Weak

Schofield et al. (2013) USA

Weak

Weak

Weak

Moderate

a

U.S. Department of Transport.

No sample size calculation Unit of analysis: organisation Low response rate (17%) Unit of analysis: jurisdictional

Unit of analysis: aggregated national fatality data No sample size calculation Unit of analysis: organisation No sample size calculation Unit of analysis: organisation Unit of analysis: organisation

No sample size calculation Unit of analysis: organisation Unit of analysis: organisation Unit of analysis: aggregated national fatality data Unit of analysis: operational district

Unit of analysis: aggregated national fatality data Unit of analysis: organisation Unit of analysis: aggregated compensation data

Types of testing programs examined not reported Frequency of testing and proportion of employees tested not reported Random testing conducted according to mandated and regulated DOTa guidelines The same testing program applied across worksites. Frequency of testing varied across worksites Types of testing programs varied across workplaces Frequency of testing and proportion of employees tested not reported 18% of study population exposed to Peer Care Random testing conducted according to mandated and regulated DOTa guidelines Types of testing programs varied across workplaces Frequency of testing and proportion of employees tested not reported Random testing conducted according to mandated and regulated DOTa guidelines Random testing conducted according to mandated and regulated DOTa guidelines Post-accident testing conducted for all accidents requiring medical attention or involving property damage ≥$250 Random testing conducted according to mandated and regulated DOTa guidelines Proportion of incumbent employees exposed to pre-employment testing not reported Types of testing programs varied across workplaces Frequency of testing and proportion of employees tested not reported

Weak

Moderate

Weak

Weak

Weak

Moderate

Moderate

Moderate

Moderate

Weak

Moderate

Moderate

Moderate

Strong

Weak

Weak

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workplace safety appears at best tenuous, and at worst, seriously flawed. 4.1. Implications for policy and practice The findings of this review also have important implications for policy and practice regarding drug testing as a workplace safety strategy. 4.1.1. Testing as a strategy for deterring employee drug use The deterrence studies reviewed all reported workplace drug testing was associated with lower drug use prevalence rates. However, methodological issues limit definitive conclusions that can be drawn from these findings. Evidence from these studies is largely based on cross-sectional designs that provide no information concerning causality. Moreover, the five cross-sectional studies provided little independent support for the deterrent effect of testing. All five studies used the same dataset (i.e., the NHSDA/NSDUH) and while data were collected over different years, these data overlapped. As a result some of these studies included the same respondents. While most deterrence studies controlled for demographic variables known to be associated with drug use (e.g., age, gender, education, income), only one study attempted to control for the effect of other strategies that are often implemented in conjunction with drug testing programs (Carpenter, 2007). Drug testing programs are rarely implemented in isolation and are often linked to written policies and employee education and training programs. These policies and programs may have an effect on employee drug consumption patterns independent of testing. Carpenter (2007) for instance found that employees in workplaces with testing reported significantly lower levels of cannabis use than employees in workplaces with no testing. However, Carpenter also observed a similar finding for employees of workplaces that did not test, but had a written policy, a drug education program, or an EAP. While the odds of reporting drug use were lower for those employed in testing workplaces compared to those employed in non-testing workplaces with a policy, education program, or an EAP, this differential effect was largely restricted to testing workplaces where a positive test resulted in instant dismissal. Therefore, it may be the outcome of drug use being detected (i.e., instant dismissal) rather than the method of detection that explains the observed difference. Such a proposition is consistent with deterrence theories that maintain immediate sanction or punishment is necessary to discourage offenders from repeating the infraction. According to deterrence theory, sanctions are seen as a necessary component to determining whether a testing program has a deterrent effect (Schaub, 2004). Frone (2013) points out that the relationship between drug testing and deterrence may also be affected by the likelihood of detection. According to Frone the likelihood of detection is a function of the biological specimen being tested, the testing rate, and the frequency and quantity of use among employees. Rather than deterring use entirely, the testing may just reduce the frequency of use to a level that positive testing rates decline but use is not eliminated (Frone, 2013). Such a hypothesis may explain the findings of Lange et al. (1994) who observed a significant reduction in positive tests rates over the 2 years period following the introduction of pre-employment screening. It is also feasible that, rather than deterring drug use, testing may motivate some employees to use drugs that are perceived to be less readily detectable than the drug types typically targeted by workplace drug testing. However, there appears to be no research that has specifically examined this issue (Frone, 2013). Recent research indicates that any such effect may be minor. Barratt et al. (2013) found only a small proportion of drug users were motivated to use synthetic cannabinoids because they believe them to be is less

detectable than cannabis. Much larger proportions were motivated by curiosity and a belief that such drugs were legal to use (Barratt et al., 2013). Another explanation is that drug testing may simply deter drug users from employment in workplaces that conduct testing. Three of the reviewed studies that reported a deterrent effect also reported that workers who were current or past drug users (including those who had not used in the past 3 years) were significantly less likely to want to work at workplaces with drug testing programs (Hoffmann and Larison, 1999; Larson et al., 2007; Zhang et al., 1999). It is feasible that rather than deterring use, workplace testing programs may deter current and past drug users from applying for jobs with companies that drug test. While this may be an acceptable outcome in the case of job applicants who are current drug users, it may be less acceptable in the case of applicants who may have occasionally used drugs several years ago, but no longer use. These individuals are unlikely to present a drug related risk to workplace safety or productivity, but their reluctance to apply for positions in workplaces that drug test may have a negative impact on safety and productivity if it reduces the potential pool of suitably qualified and experienced applicants. 4.1.2. Testing as a strategy to reduce occupational injury/accident rates Evidence concerning the effectiveness of testing in reducing occupational accidents or injuries varied between studies. Eleven reviewed studies reported testing was associated with a reduction in accident rates, three reported no associated reduction and three reported mixed results. However, most of these 17 studies suffered from methodological problems which limit conclusions that can be drawn. All utilised aggregated or ecological data concerning accident rates, which limits conclusions regarding the effects of drug testing on individual employees. Eight studies were assessed as being methodologically weak either due to the use of inappropriate cross-sectional designs, and/or selection bias and failure to control for potential confounding variables. Eight studies were assessed as demonstrating moderate methodological rigor, however, all failed to adequately control for potential confounding variables that could equally explain the reported results. For example, Spicer and Miller (2005) examined the reportable injury data of five railroad companies from 1983 to 1996 and found that the introduction of random alcohol and drug testing in the transport industry was associated with a significant decline in injury rates. However, no other relevant safety changes in the railroad industry were controlled for and data examined by Spicer and Miller indicate a significant decline in the injury rates of all five companies prior to the implementation of testing. Moreover, the focus of the study was on the evaluation of a peer intervention program (Peer Care) that was implemented in one company prior to the introduction of federally mandated random drug and alcohol testing during the study period. This Peer Care program involved education, training, and access to employee counselling and Spicer and Miller reported that this program had a significant effect on reducing injury rates prior to the introduction of testing. While injury rates continued to decline after the introduction of drug testing in 1990 and alcohol testing 1994, it is difficult to differentiate independent effects of these three interventions. Similarly, Swena and Gaines (1999) utilised an interrupted time series design to examine the impact of federally mandated random drug testing on fatal truck accidents, but failed to control for other changes in heavy road transport safety and road safety that occurred in the same time period that could also have affected fatality rates. Cashman et al. (2009) argued that the statistical analyses applied by Spicer and Miller (2005) and Swena and Gaines (1999) were not appropriate for examining the independent effects of random drug

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and alcohol testing and applied a different approach to analysing time series data that accounted for secular time trends and autocorrelation between observations. The results of Cashman et al.’s (2009) re-analysis of Spicer and Miller’s (2005) data indicated a significant decrease in the level of injuries immediately following the introduction of alcohol testing, but no significant effect on the existing long-term downward trend in injury rates. Cashman et al.’s (2009) re-analyses of both Spicer and Miller’s (2005) and Swena and Gaines’ (1999) datasets, indicated no significant decrease in injury rates immediately following the introduction of random drug testing, but a significant decline in the yearly injury rate, in addition to the already downward trend was observed over the long term. However, while Cashman et al. (2009) argue that their analyses was more appropriate, they also noted the inherent limitations of time series designs in controlling for bias resulting from co-occurring interventions and conclude that there is insufficient evidence to indicated drug and alcohol testing is effective in preventing occupational injuries. Despite these qualifications, the results of the current review indicate that random alcohol testing may have potential to reduce occupational injury rates, at least in the case of the transport industry. The one study assessed as demonstrating strong methodological rigour found random alcohol testing reduced alcohol involved road fatalities among heavy truck drivers (Brady et al., 2009). Similarly, some of the studies that demonstrated moderate methodological rigour (Miller et al., 2007; Snowden et al., 2007; Spicer and Miller, 2005) also found random alcohol testing to be associated with reductions in accidents in the transport industry. This may be due to the integrity of the random testing program as in the U.S. random testing of heavy vehicle drivers is mandated and regulated by the Federal Department of Transport. Alternatively, as indicated by the findings of Spicer and Miller (2005) and Miller et al. (2007), it may be that the potential of alcohol testing for reducing accident rates is realised when it is combined with other strategies that address workplace culture, peer interaction and other relevant factors. Without addressing such factors some types of testing programs may actually mask the true extent of safety risk by increasing employee reluctance to report minor accidents and injuries. Morantz and Mas (2008) reported that postaccident drug testing was associated with a significant decrease in workers compensation claims. However, the largest reductions were for claims that did not require time off work and for minor injury reports. The authors concluded that the threat of a drug test may have deterred workers from reporting minor injuries, rather than resulting in an actual reduction in injury rates. 4.1.3. Assumptions underlying the rationale forworkplace drug testing One reason for the lack of a strong evidence base for the efficacy of testing may be invalid assumptions underlying the rationale for testing as a workplace strategy. Frone (2013) argues that workplace testing is based on three main assumptions: (1) testing can identify most employees who use drugs; (2) a positive test result identifies employees who are likely to be impaired; and (3) there is a causal relationship between employee drug use and employee safety. However, evidence relevant to these assumptions reviewed by Frone (2013) indicated that: (1) workplace testing is only likely to identify frequent users and most employees that use drugs do so infrequently; (2) a positive drug test merely indicates past use of a drug, not impairment; and (3) the relationship between drug use, cognitive and psychomotor performance, and safety outcomes is not strong and more complex than typically acknowledged. 4.1.4. The utility of workplace drug testing The lack of a sound evidence base for the efficacy of testing is at odds with the apparent growth in the use of testing as a workplace

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safety strategy. While the proportion of US employers who conduct testing has declined from a peak in the early to mid-1990s (Frone, 2013), indicating that some employers may no longer be convinced of the usefulness of testing, nearly half the US workforce report that their employer conducts some form of drug testing (Larson et al., 2007) and support for workplace testing appears to be increasing in other countries (Nolan, 2008; Pierce, 2012). There is no doubt that the growth in the prevalence of workplace testing is related to concerns about safety and productivity and advances in testing technologies in providing relatively reliable and objective indicators of potential past and recent use of most types of commonly used illicit drugs (Moore, 2011; Phan et al., 2012). However, the extent of support and interest in testing as a workplace strategy, in light of the poor evidence base for its efficacy, indicates that there may be other explanations for growth in testing. One alternative explanation may be successful marketing efforts by the drug testing industry. It has been estimated in the US and Canada that workplace testing is at least a $2billion a year industry and increasing (Grantham, 2012). Growth in the prevalence of workplace testing may also be due to compliance with new legislation and regulations. For example, the US (Frone, 2013), Europe (Pierce, 2012), and Australia (e.g., CASR, 1998) have introduced legislation mandating drug testing in particular industries. Similarly, many countries have occupational health and safety legislation and regulations that do not mandate testing, but contain provisions that may implicitly encourage testing. Hence, some employers may introduce testing in order to comply with relevant legislation and regulations regardless of their beliefs about the efficacy of testing. Previous research has also identified that workplace drug testing can perform a symbolic function by allowing employers to control employee behaviour and manage the reputation and image of the work organisation (Brunet, 2002; Cavanaugh and Prasad, 1994; Knudsen et al., 2003). For example, the introduction of drug testing in reaction to normative pressure from the media and public opinion concerning the ‘drug problem’ allows organisations to demonstrate values and concerns that are consistent with perceived social values and concerns of the wider community (Knudsen et al., 2003). Similarly, testing can operate as a social control mechanism that enables employers to reinforce the expectation that employees should not use illegal drugs (Borg, 2000). It is likely that all these factors have played a role in the increasing use of testing as a workplace strategy. As speculated elsewhere (Galea, 2013) drug testing is based on a logical and compelling idea (i.e., that testing can reduce drug related risk by deterring drug use among employees or identifying those that use drugs) and driven by wider social concerns regarding drug use, workplace drug testing has been implemented and support for it is growing regardless of the evidence base for its effectiveness. 4.1.5. Implications for future research The findings of this review have several implications for the conduct of future research. First, much of the reviewed research was of poor methodological quality. In order to inform good policy and practice, there is a need for quality research to be undertaken that is methodologically sound. While the conduct of randomised control trials in the workplace may not be practical, the use of rigorous non-randomised experimental, cohort, case-control, or interrupted time-series designs that incorporate matched control groups and measure potential confounding variables would contribute substantially to the existing evidence base. Where more rigorous research designs are employed, emphasis should also be placed on identifying if any observed effects are of practical or clinical importance. Second, all of the research reviewed was undertaken in the US. Differences between countries in terms of industrial relations

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legislation and practices, work organisation and human resource legislation and practices, and workforce and workplace cultures create an imperative for evaluations of workplace testing to be conducted in other countries. Third, future research may need to consider other outcome measures in addition to occupational accident and injury rates. While little is known about the extent of drug related workplace accidents and injury rates (Frone, 2013), the relatively low illicit drug use prevalence rates among workforces internationally (Larson et al., 2007; Pidd et al., 2008; Smith et al., 2004), and even lower prevalence rates for drug use and impairment while at work (Frone, 2006; Pidd et al., 2011), indicate prevalence of drug related workplace accidents and injuries is also likely to be low. Low prevalence rates may limit the ability of evaluation studies to detect reductions in accident or injury rates that are of clinical or practical significance. Measures of the broader workplace safety culture or absenteeism rates and other productivity and worker well being indicators may be needed. Other measures of the effectiveness of testing could also include the consequences for individuals who return positive test results. There appears to be very little research that has examined this issue. Understanding the effects of workplace drug testing in terms of drug counselling/treatment referral pathways and outcomes, and in terms of employment outcomes, has important implications for evaluating consequences of testing for not only individual employers, but also for the broader workforce and wider community in general.

4.1.6. Limitations While the current study represents a comprehensive systematic review of research concerning the effectiveness of workplace testing to-date, it is not without limitations. First, the review is qualitative rather than quantitative and as such does not provide an overall summary of the effect of workplace testing. Lack of information concerning effect sizes in the reviewed studies meant a quantitative review was not possible. Second, there are a range of intervention study evaluation tools available to undertake systematic reviews and the quality of a review may vary according to the type of assessment tool used. Due to the wide variation in design among studies included in this review, the EPHPP tool was chosen as it was developed to evaluate a variety of intervention study designs including RCTs, pre/post and case-control studies. The EPHPP tool has been shown to compare well with a Cochrane Collaboration assessment tool (Armijo-Olivo et al., 2012) and in a comprehensive review of quality assessment tools, the EPHPP was included with seven other tools rated as the most suitable for systematic reviews (Deeks et al., 2003).

4.1.7. Conclusions In spite of the growing international interest in drug testing as a workplace policy to address drug issues, the evidence of its effectiveness is weak. Some evidence for the efficacy of random alcohol testing in the road transport industry was identified. However, in general the findings of the current review are consistent with previous reviews (Cashman et al., 2009; Frone, 2013; Kraus, 2001; Macdonald et al., 2010; Macdonald and Wells, 1994; Normand et al., 1994), and indicate that the expansion of workplace drug testing initiatives is not supported by the current evidence base. Given the growing utilisation of and support for testing as a workplace strategy, there is a pressing need for more methodologically rigorous research to evaluate the efficacy of drug testing in improving workplace safety, productivity, and worker well being.

Declaration of interests This project was funded in part by Safework South Australia, the Australian Government Department of Health, and the South Australian Department of Health. The authors do not receive direct or indirect funding or have any connection with the tobacco, alcohol, pharmaceutical or gaming industries or anybody substantially funded by one of these organisations. No other conflicts of interest are known.

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