The Netherlands remains one of Europe’s biggest users of party drugs MDMA and ketamine, according to new research based on waste water analysis in 115 cities across 25 countries.

The study, carried out by the European drugs agency EUDA using data supplied in part by Dutch water research institute KWR, found that the Netherlands ranked among the top three countries for ketamine use, alongside Belgium and Germany. Five Dutch towns and cities – Amsterdam, Utrecht, Rotterdam, Eindhoven and Nieuwegein – took part in this year’s research.

Higher levels of ketamine were recorded in Amsterdam, Eindhoven and Utrecht, while Rotterdam showed a fall but still ranked among the top 20 cities in Europe. Berlin, which took part in the study for the first time, ranked second overall, while Bristol, in England, topped the wider European ranking.

Researchers analysed daily waste water samples for a week in spring, looking for traces of drugs including cocaine, MDMA, ketamine and cannabis. The test period is chosen to avoid holidays or festivals so that results reflect normal use.

Levels of cocaine and MDMA typically rise between Friday and Monday, peaking on Sunday, which the EUDA said indicates mainly recreational use at weekends.

The Netherlands also remains the EU’s leading MDMA user with Amsterdam topping the list, although the capital recorded its first fall in MDMA traces since the coronavirus pandemic. Levels in Rotterdam were unchanged.

Antwerp again topped the European rankings for cocaine, which remains most common in western and southern European cities. Across the cities that have taken part since 2011, cocaine residues have risen steadily over time.

Cannabis remains the most widely used drug overall, with surveys suggesting more than 8% of European adults used it in the past year.

Waste water measurements showed little change compared with earlier studies, although relatively high levels were found in the Netherlands, Germany and Slovenia.

The study also looked at amphetamine and methamphetamine. Crystal meth remains rare in the Netherlands and is more common in eastern Europe, while amphetamine levels varied widely between cities.