Since March of 2020, tight measures against COVID-19, newly declared as pandemic by World Health Organization, affected almost all areas of our lives. Similarly, as with other aspects of community life, marked changes were expected to take place in the drug scene during and after the first lockdown period (16.3.2020–14.4.2020 in Finland). Wastewater-based epidemiology (WBE) is an approach established as an objective means for monitoring regional drug use. In Finland, we began WBE in 2012 with ten cities, and ended up to 27 cities (approximately 60% of Finnish population) since 2020. This study illustrates regional trends in stimulant drug use in Finland during the COVID-19 pandemic as a part of trend monitoring for up to 10 years.

Composite 24-h samples of untreated wastewater were collected twice a year during one-week sampling periods from the inlets of wastewater treatment plants. Every other year 1-2 sampling campaigns were performed in the four biggest cities only. In 2020, two extra sampling periods (total of four periods) were carried out to evaluate the impact of measures against COVID-19 on drug use. Samples were analyzed with a fully validated UHPLC-MS/MS system. Daily drug consumption was calculated from the measured concentrations of the drugs or their metabolites in wastewater.

While the stimulant drug consumption has been steadily increasing in Finland during the years of WBE, in 2020 the overall trend leveled off, with drug use being in higher level than ever before. However, the changes observed after the first quarter of 2020 varied markedly in different cities, with deepest decrease in Mariehamn, Åland, and highest increases in Lappeenranta and Vihti. During 2021, consumption of amphetamine, the dominant stimulant drug in Finland, was reduced by half from March to November/December. Instead, cocaine use remained in its newly increased level in Helsinki metropolitan area, bringing consumption of these two drugs record close to each other.

COVID-19 measures may have played a role in the leveling observed in overall stimulant drug use trend, but the changes varied regionally and remained minor and transient in most cities. It seems that drug use was less affected by lockdown in 2020, as well as other measures, than many other societal phenomena. The marked fall of amphetamine consumption observed after spring of 2021 is temporally related to large seizures of drugs, which may have exhausted drug supplies. However, it can be speculated whether COVID-19 measures may have, for their part, delayed the recovery of illicit market after the seizures. Although the overall national drug situation is by far dominated by the biggest cities with largest populations, this study with opposing drug use trends in different cities shows again the importance of including a range of cities with different sizes and geographical locations in monitoring programs, both for a realistic picture of the overall drug situation, and to be able to offer objective and comparable data to various actors of both national and local level.

Drug use was less affected by measures against COVID-19 than many other societal phenomena. To obtain a realistic picture of the multifaceted drug situation, both during normal and exceptional circumstances such as COVID-19, it is essential to include a representative and wide enough selection of cities in monitoring programs.