An innovative study reveals consumption patterns in the Spanish capital
The wastewater of Madrid has become an unexpected mirror of social behaviour, revealing drug consumption habits among its residents. A thorough analysis conducted between December 2023 and October 2025 has allowed for a detailed mapping of illegal substance use in the city, highlighting that cocaine and cannabis are the most consumed.
This study, led by researchers from the Department of Analytical Chemistry at the Complutense University, is based on a simple premise: when a person consumes drugs, part of that substance is eliminated through urine and ends up in the sewage system. From nearly 400 samples collected over 24 hours at eight treatment plants covering the 21 districts of Madrid, it has been possible to accurately measure the daily concentration of various substances.
Over time, the analysis has shown that cannabis consumption remains relatively stable throughout the week. However, other drugs associated with nightlife exhibit significant peaks during the weekends. According to Magra Cialor, the project's lead researcher, "MDMA is where this pattern is most noticeable." Furthermore, although geographical differences are not very marked, some treatment plants located in the centre record higher concentrations during the weekends.
Not only illegal drugs are present; pharmaceuticals with potential for abuse such as ketamine, lorazepam, and lormetazepam have also been detected, showing a consistent pattern over time. This suggests a significant integration of these substances into the daily life of Madrid.
Despite the high consumption recorded, Madrid presents lower levels compared to other major European cities. In concrete terms, the analysis indicates that there are 77.2 milligrams daily per 1,000 inhabitants consuming cannabis in Madrid; figures notably lower than those found in Lisbon (150.8), Barcelona (220.7), or Amsterdam (319). Regarding cocaine, Madrid also stands out for having one of the lowest consumptions among the cities analysed.
Deputy Mayor Inma Sanz has pointed out that this type of analysis can be a valuable tool for estimating widespread consumption within large urban populations. The results obtained complement data from both surveys and police reports on seizures and controls.
As Madrid continues to face the challenge of problematic consumption and addictions, these studies allow for anticipating needs within the municipal system dedicated to addiction care. In 2025, nearly 12,000 patients were treated for issues arising from both legal and illegal substance misuse.
As the Municipal Plan on Addictions (2022-2026) progresses, it is clear that understanding how these substances affect the population is crucial for developing effective strategies to address this complex social phenomenon. Research on wastewater not only provides anonymous data on collective patterns but also offers deep insight into how these substances are integrated into the daily life of Madrid.
You may also like
