The International Day Against Drug Abuse and Illicit Trafficking is being marked today.

This year's theme is "The evidence is clear: invest in prevention".

According to the United Nations, the global drug problem presents a multifaceted challenge that touches the lives of millions worldwide.

From individuals struggling with substance use disorders to communities grappling with the consequences of drug trafficking and organised crime, the impact of drugs is far-reaching and complex.

Shaun Shelly, a researcher from the Department of Family Medicine at South Africa's University of Pretoria spoke to Channel Africa reporter, Sisi Segalo about the effects of drug abuse on society and the economy.