The three gateway drugs are nicotine, alcohol and cannabis. The concept is based on the “gateway hypothesis,” which states that adolescents who experiment with these drugs are more likely to use other addictive drugs later in life.  The controversy and conflicting research can be confusing, but some conclusions can still be made: Alcohol does increase the likelihood of other drug use, including the other gateway drugs (tobacco and cannabis). Addiction is a complex disease – prior use of alcohol is simply another risk factor among many, and there is no single explanation for why someone becomes addicted. The interrelationships between the gateway drugs (tobacco, alcohol and cannabis) are complex. Targeting alcohol use in adolescents will likely impact the development of other substance use disorders later in life.