A new study indicates that teens and their parents don't tell the truth when asked about their use of cocaine and opiates, even if they are told they will be drug-tested and their responses kept confidential, HealthDay reported Oct. 25.

The study, led by Virginia Delaney-Black, M.D., a pediatrics professor at Children's Hospital of Michigan, compared survey responses collected from over 200 teens and over 200 adult caregivers (mostly mothers) with the results of hair tests for drug use. Participation in the study was limited to African-American families who had received care at one urban antenatal clinic.

Hair tests on the teens showed that 30 percent had used cocaine, whereas only one percent reported it. Hair tests from parents showed that 28 percent had used cocaine, but only about six percent said they had. Results for opiates were similar.

Other studies have shown that adults underreport their own substance use, but very few comparable studies have been done on teens who are not in the court system or in treatment. Estimates of national prevalence rates of teen use outside of the court system or clinical settings are based on data collected anonymously and on what teens report about their use; the new study suggests that the estimates may be too low. 

Delaney-Black said that the results of the study should be useful for pediatricians. “If you think it's important to know whether a kid is doing drugs — specifically heroin, prescription pain killers or cocaine — then don't rely on what the teens report,” she said.

The research “generally reinforces what we know from work in adults, which is that people are usually less honest about substance use than we hope,” said Ty S. Schepis, a psychology professor at Texas State University at San Marcos.

The study, “'Just Say “I Don't': Lack of Concordance Between Teen Report and Biological Measures of Drug Use,” appeared online Oct. 25 in Pediatrics and will appear in the November 2010 print issue.