Adolescent substance use is a serious public health issue, with 5% of 8th graders (ages 13–14) reporting cannabis use in the past year. The numbers are even higher for alcohol and nicotine use, with 26% admitting to drinking and 23% to smoking nicotine. As is standard, these numbers are derived from self-report.
But a multidisciplinary team of experts led by Natasha Wade wondered if the self-report technique was accurate enough given the seriousness of the situation.
“It’s vital that we understand the factors that lead to drug use in teenagers, so that we can design targeted health initiatives to prevent children from being exposed to drugs at a young age,” said Wade, an assistant professor of psychology at the University of California, San Diego.
Wade’s hunch was correct, as her new paper in the American Journal of Drug and Alcohol Abuse shows a 9% increase in substance use numbers when hair analysis results are added to self-reporting results.
For the study, researchers asked 1,390 children whether they had taken drugs in the last year. Hair samples were then also taken so that independent tests could confirm whether recent drug-taking had taken place.
Of the children who were asked if they had taken drugs, 10% agreed that they had. Hair analyses also showed that 10% of adolescents overall tested positive for at least one drug—however, the children that self-reported drug-taking were not the same as those who tested positive through hair samples.
In fact, of the 136 cases that self-reported substance use and the 145 hair samples that were positive, matches were found for only 23 cases. Most importantly, hair drug analysis revealed an additional 9% of substance use cases over and above self-report alone, nearly doubling the number of identified substance users to 19%.
Cannabinoids were most commonly positive (6.1%), followed by alcohol (1.9%), non-prescription amphetamines (1.9%), and cocaine (1.7%). Less than 1% of participants tested positive for nicotine, opiates or fentanyl, and no participants were positive for benzodiazepines or PCP.
The hair analysis results for cannabinoids detected both THCCOOH and specific parent analytes, such as THC and CBD, with THC representing the largest single drug analyte (4.6%) followed by THCCOOH (2%). THCCOOH is necessary to confirm ingestion of cannabis, while THC or CBD may indicate cannabis use or environmental (e.g., secondhand) exposure. While the numbers make cannabis the most frequently used substance, it was rarely self-reported.
Additionally, the research team randomly selected and tested 103 samples of hair from adolescents deemed low-risk. While all low-risk participants denied any substance use, hair analysis showed 7% were confirmed positive for one or two drug classes. Cases were positive for cannabinoids, alcohol, cocaine and/or nicotine.
Given the discrepancies across the board, Wade and her team are recommending that all future research combine both self-reporting and hair analysis techniques.
“Rather than scrapping self-reporting of drug use altogether, a more accurate picture of teenage substance use can be gained by measuring both,” said Wade.
Self-reporting still has its own strengths. For instance, young people may be more willing to disclose substance use at a low level, but are less likely to when frequent drug-taking patterns emerge. Conversely, hair assays are not sensitive enough to detect only one standard drink of alcohol or smoking one cannabis joint. Instead, the method is better at detecting frequent and moderate to heavy drug use.
“Combining both methodologies is therefore vital to accurately determine the levels of substance use in the teenage population,” concluded Wade.
The hair samples were screened by FDA-cleared immunoassays or directly by LC-MS/MS, and presumptive positives were confirmed and quantified by LC-MS/MS or GC-MS/MS analysis. Tested drug classes included alcohol, amphetamines, benzodiazepines, cannabinoids, cocaine, fentanyl, opioids, nicotine, and phencyclidine.