Substance use in individuals with mild to borderline intellectual disability: A comparison between self-report, collateral-report and biomarker analysis

https://doi.org/10.1016/j.ridd.2016.04.006Get rights and content

Highlights

  • We assessed substance use using self-report, collateral-report, and biomarkers.

  • Willingness to participate in self-report was higher than in biomarker sampling.

  • Substance use rates in MBID from self-report and collateral-report were similar.

  • Self-reported use in MBID was not lower compared to positive biomarker results.

  • Biomarker analysis had limited additional value to self-report.

Abstract

Background and aims

Individuals with mild or borderline intellectual disability (MBID) are at risk of substance use (SU). At present, it is unclear which strategy is the best for assessing SU in individuals with MBID. This study compares three strategies, namely self-report, collateral-report, and biomarker analysis.

Methods and procedures

In a sample of 112 participants with MBID from six Dutch facilities providing care to individuals with intellectual disabilities, willingness to participate, SU rates, and agreement between the three strategies were explored. The Substance use and misuse in Intellectual Disability − Questionnaire (SumID-Q; self-report) assesses lifetime use, use in the previous month, and recent use of tobacco, alcohol, cannabis, and stimulants. The Substance use and misuse in Intellectual Disability − Collateral-report questionnaire (SumID-CR; collateral-report) assesses staff members' report of participants' SU over the same reference periods as the SumID-Q. Biomarkers for SU, such as cotinine (metabolite of nicotine), ethanol, tetrahydrocannabinol (THC), and its metabolite THCCOOH, benzoylecgonine (metabolite of cocaine), and amphetamines were assessed in urine, hair, and sweat patches.

Results

Willingness to provide biomarker samples was significantly lower compared to willingness to complete the SumID-Q (p < 0.001). Most participants reported smoking, drinking alcohol, and using cannabis at least once in their lives, and about a fifth had ever used stimulants. Collateralreported lifetime use was significantly lower. However, self-reported past month and recent SU rates did not differ significantly from the rates from collateral-reports or biomarkers, with the exception of lower alcohol use rates found in biomarker analysis. The agreement between self-report and biomarker analysis was substantial (kappas 0.60–0.89), except for alcohol use (kappa 0.06). Disagreement between SumID-Q and biomarkers concerned mainly over-reporting of the SumID-Q. The agreement between SumID-CR and biomarker analysis was moderate to substantial (kappas 0.48 − 0.88), again with the exception of alcohol (kappa 0.02).

Conclusions and implications

In this study, the three strategies that were used to assess SU in individuals with MBID differed significantly in participation rates, but not in SU rates. Several explanations for the better-than-expected performance of self- and collateral-reports are presented. We conclude that for individuals with MBID, self-report combined with collateralreport can be used to assess current SU, and this combination may contribute to collaborative, early intervention efforts to reduce SU and its related harms in this vulnerable group.

Section snippets

What this paper adds?

This paper is the first to compare three strategies to assess substance use among individuals with mild to borderline intellectual disability: self-report with a questionnaire developed for this population (i.e., SumID-Q), collateral-report by staff members, and biomarker analysis of urine, hair and sweat patch samples. We found that biomarker analysis was of limited additional value compared to self-report or collateral-report in the assessment of substance use, especially given the additional

Participants

Between November 2011 and December 2012, six organizations of the Dutch Association of Healthcare Providers for People with Disabilities invited 135 individuals with intellectual disabilities (ID) who had access to substances to participate. Two individuals refused to participate for unspecified reasons, three had no MBID, one individual withdrew consent during the SumID-Q interview and caregivers of two individuals withdrew consent to participate. Whilst 127 individuals (94%) completed the

Differences between SumID-Q and biomarker analysis in willingness to participate

In addition to the fifteen individuals who refused to provide any biomarkers, several were not willing to participate in either the urine analysis or the hair/sweat patch analysis. This resulted in significantly lower biomarker participation (77% for urine sampling, 62% for hair or sweat patch sampling) compared to SumID-Q participation (94%, χ2(2, n = 135) = 39.95, p < 0.001). Post hoc tests revealed that willingness to participate in the SumID-Q was significantly higher compared to both the urine

Discussion

In this study, we compared self-reported SU (SumID-Q), collateral-report by staff members (SumID-CR), and urine, hair, and sweat patches collected from a sample of 112 individuals with MBID. To our knowledge, this is the first study to compare these strategies to assess SU in individuals with MBID.

Irrespective of the assessment strategy, high rates of alcohol and tobacco use and slightly lower – but nonetheless substantial – illicit drug use rates were found. In fact, with the exception of

Competing interests

None.

Acknowledgements

This study was funded by ZonMW, The Netherlands Organisation for Health Research and Development (project number 60-60600-97-158). The authors wish to thank participants, institutions, and research assistants for their contributions, and Neil B. McGillicuddy, Eric O. Noorthoorn, and Neomi van Duijvenbode for supporting this study and proofreading this manuscript.

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