Matthias Pierce

Impact of treatment for opioid dependence on fatal drug-related poisoning: a national cohort study in England

Abstract Aims To compare the change in illicit opioid users’ risk of fatal drug‐related poisoning (DRP) associated with opioid agonist pharmacotherapy (OAP) and psychological support, and investigate the modifying effect of patient characteristics, criminal justice system (CJS) referral and treatment completion. Design National data linkage cohort study of the English National Drug Treatment Monitoring System and the Office for National Statistics national mortality database. Data were analysed using survival methods. Setting All services in England that provide publicly funded, structured treatment for illicit opioid users. Participants Adults treated for opioid dependence during April 2005 to March 2009: 151 983 individuals; 69% male; median age 32.6 with 442 950 person‐years of observation. Measurements The outcome was fatal DRP occurring during periods in or out of treatment, with adjustment for age, gender, substances used, injecting status and CJS referral. Findings There were 1499 DRP deaths [3.4 per 1000 person‐years, 95% confidence interval (CI) = 3.2–3.6]. DRP risk increased while patients were not enrolled in any treatment [adjusted hazard ratio (aHR) = 1.73, 95% CI = 1.55–1.92]. Risk when enrolled only in a psychological intervention was double that during OAP (aHR = 2.07, 95% CI = 1.75–2.46). The increased risk when out of treatment was greater for men (aHR = 1.88, 95% CI = 1.67–2.12), illicit drug injectors (aHR = 2.27, 95% CI = 1.97–2.62) and those reporting problematic alcohol use (aHR = 2.37, 95% CI = 1.90–2.98). Conclusions Patients who received only psychological support for opioid dependence in England appear to be at greater risk of fatal opioid poisoning than those who received opioid agonist pharmacotherapy.

National record linkage study of mortality for a large cohort of opioid users ascertained by drug treatment or criminal justice sources in England, 2005–2009

Highlights • Opioid user mortality is almost 6 times higher than in the general population.• Mortality is elevated for a range of diseases and for homicide and suicide.• Excess mortality persists into old age and for some causes is exacerbated.• Drug-related poisoning (DRP) accounts for just under a half of opioid user deaths.• Young female DRP mortality is lower than male but the difference narrows with age.

Drug spend and acquisitive offending by substance misusers

AIM The need to generate income to fund drug misuse is assumed to be a driver of involvement in acquisitive crime. We examined the influence of drug misuse expenditure, and other factors, on acquisitive offending. METHODS Clients (N=1380) seeking drug treatment within 94 of 149 Drug Action Teams (DATs) across England completed a comprehensive survey, incorporating validated scales and self-report measures, such as levels of drug and alcohol use and offending. RESULTS Forty per cent (N=554) had committed acquisitive crime in the previous month. Regression analysis showed that acquisitive offending was associated with the presence of problematic use of crack cocaine, poly-drug use, sharing injecting equipment, unsafe sex, overdose risk, higher drug spend, unemployment, reduced mental wellbeing, and younger age. CONCLUSIONS Rates of acquisitive crime among drug users are high. Drug using offenders can be distinguished from drug using non-offenders by problematic crack cocaine use, younger age, income-related factors, and indicators of a chaotic life style and complex needs. Behavioural and demographic factors were associated more strongly with acquisitive crime than drug use expenditure, suggesting that the need to finance drug use is not necessarily the main factor driving acquisitive offending by drug users.

Quantifying crime associated with drug use among a large cohort of sanctioned offenders in England and Wales

Highlights • Opiate use is associated with elevated (acquisitive and non-acquisitive) offending.• The association between drug use and crime is stronger for women than men.• Cocaine use is associated with offending among males but not among females.• Opiate and cocaine use is associated with 25 times the rate of prostitution (females only).

Problem drug use prevalence estimation revisited: heterogeneity in capture-recapture and the role of external evidence

Abstract Background and Aims Capture–recapture (CRC) analysis is recommended for estimating the prevalence of problem drug use or people who inject drugs (PWID). We aim to demonstrate how naive application of CRC can lead to highly misleading results, and to suggest how the problems might be overcome. Methods We present a case study of estimating the prevalence of PWID in Bristol, UK, applying CRC to lists in contact with three services. We assess: (i) sensitivity of results to different versions of the dominant (treatment) list: specifically, to inclusion of non‐incident cases and of those who were referred directly from one of the other services; (ii) the impact of accounting for a novel covariate, housing instability; and (iii) consistency of CRC estimates with drug‐related mortality data. We then incorporate formally the drug‐related mortality data and lower bounds for prevalence alongside the CRC into a single coherent model. Results Five of 11 models fitted the full data equally well but generated widely varying prevalence estimates, from 2740 [95% confidence interval (CI) = 2670, 2840] to 6890 (95% CI = 3740, 17680). Results were highly sensitive to inclusion of non‐incident cases, demonstrating the presence of considerable heterogeneity, and were sensitive to a lesser extent to inclusion of direct referrals. A reduced data set including only incident cases and excluding referrals could be fitted by simpler models, and led to much greater consistency in estimates. Accounting for housing stability improved model fit considerably more than did the standard covariates of age and gender. External data provided validation of results and aided model selection, generating a final estimate of the number of PWID in Bristol in 2011 of 2770 [95% credible interval (Cr‐I) = 2570, 3110] or 0.9% (95% Cr‐I = 0.9, 1.0%) of the population aged 15–64 years. Conclusions Steps can be taken to reduce bias in capture–recapture analysis, including: careful consideration of data sources, reduction of lists to less heterogeneous subsamples, use of covariates and formal incorporation of external data.

Problem drug use prevalence estimation revisited

Abstract Background and Aims Capture–recapture (CRC) analysis is recommended for estimating the prevalence of problem drug use or people who inject drugs (PWID). We aim to demonstrate how naive application of CRC can lead to highly misleading results, and to suggest how the problems might be overcome. Methods We present a case study of estimating the prevalence of PWID in Bristol, UK, applying CRC to lists in contact with three services. We assess: (i) sensitivity of results to different versions of the dominant (treatment) list: specifically, to inclusion of non‐incident cases and of those who were referred directly from one of the other services; (ii) the impact of accounting for a novel covariate, housing instability; and (iii) consistency of CRC estimates with drug‐related mortality data. We then incorporate formally the drug‐related mortality data and lower bounds for prevalence alongside the CRC into a single coherent model. Results Five of 11 models fitted the full data equally well but generated widely varying prevalence estimates, from 2740 [95% confidence interval (CI) = 2670, 2840] to 6890 (95% CI = 3740, 17680). Results were highly sensitive to inclusion of non‐incident cases, demonstrating the presence of considerable heterogeneity, and were sensitive to a lesser extent to inclusion of direct referrals. A reduced data set including only incident cases and excluding referrals could be fitted by simpler models, and led to much greater consistency in estimates. Accounting for housing stability improved model fit considerably more than did the standard covariates of age and gender. External data provided validation of results and aided model selection, generating a final estimate of the number of PWID in Bristol in 2011 of 2770 [95% credible interval (Cr‐I) = 2570, 3110] or 0.9% (95% Cr‐I = 0.9, 1.0%) of the population aged 15–64 years. Conclusions Steps can be taken to reduce bias in capture–recapture analysis, including: careful consideration of data sources, reduction of lists to less heterogeneous subsamples, use of covariates and formal incorporation of external data.

Pathways through opiate use and offending: a systematic review

Background Although evidence points to a strong link between illicit drug use and crime, robust evidence for temporal order in the relationship is scant. We carried out a systematic review to assess the evidence for pathways through opiate/crack cocaine use and offending to determine temporal order. Methods A systematic review sourced five databases, three online sources, bibliographies and citation mapping. Inclusion criteria were: focus on opiate/crack use, and offending; pre-drug use information; longitudinal design; corroborative official crime records. Rate ratios (RR) of post-drug use initiation to pre-drug use initiation were pooled using random effects meta-analysis. Results 20 studies were included; UK (9) and US (11). All were of opiate use. Mean age at (recorded) offending onset (16.7 yrs) preceded mean age at opiate-use onset (19.6 yrs). Substantial heterogeneity (over 80%: unexplained by meta-regression) meant that RRs were not pooled. The RR for total (recorded) offending ranged from 0.71 to 25.7 (10 studies; 22 subsamples: positive association, 4: equivocal, 1: negative association). Positive associations were observed in 14/15 independent samples; unlikely to be a chance finding (sign test p = 0.001). Individual offence types were examined: theft (RR 0.63–8.3, 13 subsamples: positive, 9: equivocal, 1 negative); burglary (RR 0.74–50.0, 9 subsamples: positive, 13: equivocal); violence (RR 0.39–16.0, 6 subsamples: positive, 15: equivocal); and robbery (RR 0.50–5.0, 5 subsamples: positive, 15: equivocal). Conclusions Available evidence suggests that onset-opiate use accelerates already-existing offending, particularly for theft. However, evidence is out of date, with studies characterised by heterogeneity and failure to use a matched non-opiate-user comparison group to better-establish whether onset-opiate use is associated with additional crime.

Factors associated with receipt of residential rehabilitation by opiate users indicate that these clients are more amenable to drug treatment

Aims: Residential rehabilitation (RR) is relatively expensive and is received by a minority of drug users seeking treatment. It is perceived to be particularly effective, but those entering RR may be more amenable to treatment than those treated in other modalities. The objective of this study was to explore ways in which opiate users treated in a residential setting differ, at treatment entry, from those treated in a community setting. Methods: Opiate users (N = 406) who received either RR or community substitute prescribing (CSP) were sampled from the UK Drug Treatment Outcomes Research Study (DTORS). A logistic regression analysis, controlling for Drug Action Team, was used to predict the occurrence of RR versus CSP for the treatment of opiate dependence. Measures included self-reported levels of drug use, offending, social measures and health. Findings: RR clients were different to CSP clients in a number of respects that may positively influence treatment outcome; most importantly, their reasons for seeking treatment were different and they were better motivated. Conclusions: Higher treatment motivation may be one factor that explains why RR is a more effective treatment for clients with complex drug-related problems.

Short-Term Outcomes for Opiate and Crack Users Accessing Treatment: The Effects of Criminal Justice Referral and Crack Use.

Background/Aims: The English drug treatment population doubled in size between 1998 and 2008, increasingly characterised by crack cocaine use and criminal justice system (CJS) referral. We assessed short-term (median 3.5 month) behaviour changes following participation in drug treatment and the moderating effect of CJS referral/crack use. Methods: Opiate and/or crack cocaine users (n = 1,267) were recruited from 342 agencies. Outcome effects were assessed via interaction term regression, clustered at participant level, controlling for client characteristics. Treatment retention effects were tested via Cox proportional hazard models. Results: Statistically significant improvements in health, drug use and offensive behaviour were observed (e.g. heroin use from 87 to 51%, acquisitive offending from 47 to 23%). Referral route was not associated with variation in outcomes. Crack use at baseline was associated with a greater chance of non-fatal overdose at follow-up (p = 0.035, 95% CI 1.08-8.20) but a greater reduction in offending income (p = 0.002, 95% CI £104-£419). Conclusion: Despite changes in the English drug treatment population, equivalent short-term improvements in client behaviour were observed a decade earlier. Outcomes for CJS-referred clients were comparable to non-CJS. Crack use at treatment entry offered some scope for greater improvements in offending but may be a barrier to cessation of mortality-associated risky behaviour.

Confounding in longitudinal studies in addiction treatment research

Abstract Background: The effectiveness of treatment for people with substance use disorders is usually examined using longitudinal cohorts. In these studies, treatment is often considered as a time-varying exposure. The aim of this commentary is to examine confounding in this context, when the confounding variable is time-invariant and when it is time-varying. Method: Types of confounding are described with examples and illustrated using path diagrams. Simulations are used to demonstrate the direction of confounding bias and the extent that it is accounted for using standard regression adjustment techniques. Results: When the confounding variable is time invariant or time varying and not influenced by prior treatment, then standard adjustment techniques are adequate to control for confounding bias, provided that in the latter scenario the time-varying form of the variable is used. When the confounder is time varying and affected by prior treatment status (i.e. it is a mediator of treatment), then standard methods of adjustment result in inconsistency. Conclusions: In longitudinal cohorts where treatment exposure is time varying, confounding is an issue which should be considered, even if treatment exposure is initially randomized. In these studies, standard methods of adjustment may result be inadequate, even when all confounders have been identified. This occurs when the confounder is also a mediator of treatment. This is a likely scenario in many studies in addiction.