Drug addiction can start for various reasons and there is no one definitive answer to where it starts. It can be due to a combination of genetic, environmental, and personal factors. Some people may start using drugs as a way to cope with emotional or physical pain, while others may start using drugs recreationally or experimentally. Drug addiction can occur at any age, but it often starts during adolescence or young adulthood. It is important to seek help if you or someone you know is struggling with drug addiction.