A huge gap is opening up in the country's illicit drugs market, as cash-strapped users switch to generic stimulants while wealthier buyers in search of a high opt for "premium" products. A paper to be published in the online edition of Drugs and Alcohol Today has found that young adults are turning to unidentified white powders following the ban on mephedrone, the former "legal high", and the decline in the purity of popular street drugs such as cocaine.