Drug use in Europe remains high even though the consumption of cannabis and cocaine appears to be slowing, as is new heroin use, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) said in its annual report.
"New synthetic drugs and patterns of use are appearing, both on the illicit drug market and in the context of non-controlled substances," the Lisbon-based centre said in its report.
"The Internet presents growing challenges, both as a mechanism for rapid diffusion of new trends and as a burgeoning anonymous marketplace with global reach."
The centre said more chemical or natural substances were emerging on the market, with 73 new psychoactive substances detected in 2012 -- compared to just 49 in 2011 -- many of them close to cannabis due to high demand.
"A recent development is an increasing proportion of substances reported that are from less known and more obscure chemical groups," the report said.
"Many of the products on sale contain mixtures of substances, and the lack of pharmacological and toxicological data means it is hard to speculate on long term health implications of use."
Mephedrone, a party drug often called "meow meow" described as a mix between amphetamines, cocaine and ecstasy, is an example of a new drug that has become a sought-after substance on the illicit stimulant market.
"Today's drug market appears to be... less structured around plant-based substances shipped over long distances to consumer markets in Europe," the report said.
Altogether, around a quarter of Europe's adult population has used an illicit drug at some point in their lives.
And while the practice of injecting drugs is slowing, the report says figures show the long-term decline in the number of new HIV diagnoses in Europe could be interrupted as a result of outbreaks among drug users in Greece and Romania.
The report however welcomed that a record number of people -- an estimated 1.2 million -- had received treatment for illicit drug use in Europe during 2011.