(CNN) - When it comes to telling the truth about illicit drug use, kids and parents have more in common than they care to admit.
Researchers found that even when they know they will be tested for the drug, parents and their children significantly underestimate their own drug use.
In a recent study published in the journal "Pediatrics," researchers surveyed more than 400 high-risk urban teens from low socio-economic backgrounds. They also questioned their parents and guardians, who were mostly female.
After asking about drug use in a questionnaire, teen and parent hair samples were tested. The data found that young people were 52 percent more likely to test positive for cocaine in their hair samples than they were to actually report using cocaine on their questionnaires.
The study also found that parents, like their children, significantly underreported their own cocaine use. Parents were more than six times more likely to test positive for cocaine use in a hair sample and more than five times more likely to test positive for opiates than they were to report using those drugs in the questionnaire.
The researchers also found that parents played down their teens' drug use, leading the study authors to believe that questioning parents about drugs is not the best way to estimate substance use. They said other test methods are necessary to gauge the real extent of teen drug abuse.