Parents walkingParents are more concerned about their teens' mental health than about their use of drugs or alcohol, a new survey finds.

While 65 percent of 3,100 parents surveyed said they are concerned their teen suffers from anxiety or depression, more than three-quarters say they think their teen never uses drugs or alcohol, according to the survey by Silver Hill Hospital in New Canaan, Connecticut.

The Centers for Disease Control and Prevention has found that 66 percent of students say they have had at least one drink of alcohol, and 41 percent of students have used marijuana at least once, Yahoo Parenting reports.

"This reflects a dramatic underestimate of teenage substance use and again points toward the need for education for parents both with respect to communicating with their teens about drug and alcohol use as well as looking for telltale signs of drug and alcohol consumption," said Dr. Aaron Krasner, an adolescent medicine specialist at Silver Hill.

The survey found almost half of parents said their teens had told them they are depressed, anxious, or overwhelmed. Yet just 20 percent of teens whose parents were surveyed had been diagnosed with anxiety, depression or attention deficit hyperactivity disorder. Only 9 percent of parents said their teens were taking medication for any of those disorders, according to The Daily News.

"I think there's a disconnect between (parents) worrying about the problem and doing something about it," Krasner said.

About one-third of parents surveyed said they had avoided talking with their teens about sex.

Krasner advises parents to acquaint themselves with their teens' use of social media, in order to stay on top of their activities. "There are worlds upon worlds in social media and the Internet that parents are just not aware of," he said.