Only half of parents of children who drink know what their kids are up to, and similar numbers overlook their children's use of tobacco and marijuana, according to researchers at Washington University in St. Louis.

CBC News reported Sept. 24 that interviews of 600 adolescents and their parents found that 54 percent of the youths used alcohol, 44 percent smoked, and 23 percent used marijuana. But when asked about their kids' use of these substances, only 50 percent of the parents of users knew their children drank, 55 percent knew about their smoking, and 47 percent knew their children had used marijuana.

Further, only 28 percent of parents were aware of their children's use of cocaine or methamphetamine. Researchers said that the younger the children were, the more likely their parents were to miss signs of drug use.

The findings were contrasted with a previous study showing that parents were generally aware that their children were suffering from attention-deficit disorder. The authors suggested that symptoms of addiction-related problems may be harder for parents to spot. "Things like feelings of worthlessness or loss of interest in favorite activities can be very troubling to a child, but they don't necessarily impact others and might go unnoticed unless the child chooses to talk about them," said co-author Laura Jean Bierut.

The research appears in the October 2006 issue of the journal Alcoholism: Clinical & Experimental Research.