Is cannabis a gateway drug?

The "gateway drug" hypothesis — that cannabis use leads to harder drug use — is one of the most debated topics in addiction science. The evidence shows: (1) Most cannabis users do not progress to harder drugs. (2) There is a statistical association between cannabis use and subsequent use of other substances, but correlation does not imply causation. (3) The same risk factors (genetics, trauma, peer environment, mental health) that predispose to cannabis use also predispose to other substance use. (4) Animal studies show THC exposure during adolescence increases sensitivity to opioids and cocaine, suggesting a neurobiological mechanism. (5) In jurisdictions that have legalized cannabis, rates of other drug use have not consistently increased. The current scientific consensus is that cannabis is not a pharmacological gateway drug, but it may be a social or behavioral gateway in some contexts.