Does your child spend hours surfing the net? Beware, it may increase the youngster's chances of taking drugs and indulging in unprotected sex, a new study has claimed.

Researchers at the Queen's University in Canada found that young adults who are regularly glued to their screens are far more likely to engage in risky behaviour than their peers.

Such teenagers, the researchers found, were 50 per cent more likely to engaged in six "multi-risk behaviours", such as smoking, drunkenness, drug use, having unprotected sex and not using seat belts, the Daily Mail reported.

Study author Valerie Carson said that their research was "based on social cognitive theory, which suggested that seeing people engaged in a behaviour is a way of learning that behaviour".

"Since adolescents are exposed to considerable screen time -- over 4.5 hours on average each day -- they are constantly seeing images of behaviours they can then potentially adopt."

One explanation behind the findings, according to the researchers, is that a considerable amount of advertising that used to be shown on TV is now being shown on the Internet.

In addition, computer usage by adolescents has increased considerably in recent years, they pointed out.

Carson said: "TV and video games have more established protocols in terms of censorship, but Internet protocols aren't as established.

"Parents can make use of programs that control access to the Internet, but adolescents in this age group are quite savvy about technology and the Internet.

"It's possible that these types of controls are not effective in blocking all undesirable websites."

The researches also suggested that future studies should examine the specific content adolescents are being exposed to in order to help strengthen current screen time guidelines for youth.

The new findings were published in the Journal of Preventative Medicine.