I believe the answer is: are the leading causes of death and disability
The six key risk behaviours include unintentiaonal injuries, risky sexual behaviours, alcohol and drug abuse, Smoking, unhealthy diet, and lack of physical activities. The effect of these risky behaviours tend to be felt years later after teenagers become too addicted to it, which is why a lot of teenagers do not take this risk warning seriously.
When developing school health curriculum, the CDC recommends emphasizing six key risk behaviors because the behaviors are the leading causes of death and disability.
