Philosophiae Doctor - PhD / Substance abuse among adolescents is a Public Health concern globally with approximately 25 million adolescents (aged 13-15 years) who smoke tobacco, one in every ten girls and one in every five boys. In low- and middle-income countries, 14 % of girls and 18% of boys (13-15years old) are engaged in alcohol use. The Global Status Report on Alcohol and Health of 2018, reports that among the 15- to 19-year-olds, greater than a quarter were current alcohol drinkers. Cannabis (marijuana/dagga) is highly used globally with approximately 3.8% between 15 and 64 years, about 188 million people used it once or more times in 2017. The most commonly abused substances are alcohol, tobacco, and cannabis (marijuana/dagga). In South Africa, most adolescents are found in schools and the average age of drug experimentation is 12 years with early onset of use at about ten years of age.