Among young adults, self-reported illicit substance and nonmedical prescription drug use was underestimated compared with results from hair tests. These findings were published in the Journal of the American Academy of Child & Adolescent Psychiatry.
Investigators from the University of Zurich sourced data for this study from the Zurich Project on the Social Development from Childhood to Adulthood, which recruited children (N=1675) from 56 primary schools in Switzerland in 2004. In 2010, at aged 20 years, the original participants were contacted and asked to self-report drug and substance use and to give 3 cm of proximal hair. Hair samples were successfully collected from 1002 participants. Results from self-reported substance use and data from hair analyses were compared.
The participants had a mean age of 20.57 (SD, 0.38) years at hair collection, 50.2% were women, 91.1% provided a hair sample from their scalp, and 19.6% had treated their hair with bleach.
At self-report, 18.6% endorsed weekly or daily cannabis use, 7.19% ecstasy or 3,4-methylenedioxymethamphetamine (MDMA) use, 6.6% cocaine use, 5.9% codeine use, 3.7% amphetamine use, 2.9% opioid painkiller use, and 0.9% ketamine use.
The positivity rates during hair testing were 14.2% for cannabis, 12.2% for ecstasy or MDMA, 11.3% for codeine, 9.4% for cocaine, 2.6% for opioid painkillers, 2.3% for ketamine, and 1.9% for amphetamines.
Compared between self-report and laboratory testing, the highest agreement was observed for ketamine (98.2%) and the lowest agreement was observed for codeine (88.6%).
In general, 15% of participants underreported use and 8% overreported use. A total of 46 individuals underreported cocaine use and 84 individuals underreported codeine use.
In the full model, cocaine underreporting was less likely among individuals with attention-deficit/hyperactivity disorder symptoms (odds ratio [OR], 0.43; 95% CI, 0.21-0.89; P =.022) or a history of delinquency (OR, 0.78; 95% CI, 0.65-0.94; P =.007). For underreporting of codeine use, individuals with low self-control (OR, 0.22; 95% CI, 0.07-0.71; P =.012) or internalizing symptoms (OR, 0.43; 95% CI, 0.24-0.77; P =.005) were less likely to underreport.
This study was limited by the fact that the motivation for underreporting could not be determined. Individuals could have intentionally underreported or could have been mistakenly exposed.
Study authors concluded, “Both self-reports and biological testing can provide unique information on substance use. […] Our findings suggest that a combination of self-reports with hair tests may be most beneficial in sub-samples with presumably occasional substance use.”
Steinhoff A, Shanahan L, Bechtiger L, et al. When substance use is underreported: comparing self-reports and hair toxicology in an urban cohort of young adults. J Am Acad Child Adolesc Psychiatry. 2023;S0890-8567(23)00045-X. doi:10.1016/j.jaac.2022.11.011