A study conducted by the US Substance Abuse and Mental Health Services Administration (SAMHSA) found that individuals who had started taking drugs early on in life were more likely to develop mental disorders and become polydrug users. At the time of clinical admission, three quarters of drug users between 18 and 30 years of age had started taking drugs at age 17 or younger. A tenth of drug users had started at an even earlier age. 78.1% of drug users that had started taking drugs at age 11 or younger were taking more than one drug compared to 30.4% of individuals that had initiated drug use after the age of 25. 38.6% of drug users that had begun taking drugs at age 11 or under had developed some form of mental disorder. These results underline the importance of prevention programmes in childhood and early adolescence, phases that are critical for young people’s development.