One of the ways is to carry out education and promotion-
To raise the awareness of drug abuse being an issue of the society,encourage the general to reach out to those in addiction,by showcasing the symptoms and behaviors, also telling the consquences of improper drug use such as damage to the vital organs,premature death etc. as an alarm. Health care professionals can take on the role as it would be more persuasive for a professional to promote these.
Education, especially for teenagers who are the most likely to become a drug addict due to peer pressure, the stress and frustration of daily life or school, or simply curiosity. To educate talks and lessons could be carry out, to not only preventing them from drug abusing by telling the consequences but also how they could reject and avoid them, hence decreasing the risk.
Hope it helps!
