Increased incidence of smoking, alcohol and drug abuse in children and teenagers. Over a third of children try smoking by age 11 due to influence of older siblings and friends. Smoking and exposure to secondhand smoke increases risks of respiratory illnesses. Regular drug use in children can cause mood swings, loss of interest in activities, and missing items from home. Parents are the most important influence and should communicate openly with children, get to know their friends, and encourage alternative activities to prevent substance abuse issues.