Societal costs of illegal drug use in Sweden

Background: Illegal drug use is a public health concern with far-reaching consequences for people who use them and for society. In Sweden, the reported use of illegal drugs has been growing and the number of drug-induced deaths is among the highest in Europe. The aim of this study was to provide a comprehensive and up-to-date estimation of the societal costs of illegal drug use in Sweden, relying as much as possible on registry and administrative data. Methods: A prevalence-based cost-of-illness study of illegal drug use in Sweden in 2020 was conducted. A societal approach was chosen and included direct costs (such as costs of health care, social services, and the criminal justice system), indirect costs (such as lost productivity due to unemployment and drug-induced death), and intangible costs (such as reduced quality of life among people who use drugs and their family members). Costs were estimated by combining registry, administrative, and survey data with unit cost data. Results: The estimated societal costs of illegal drug use were 3.7 billion euros in 2020. This corresponded to 355 euros per capita and 0.78 % of the gross domestic product. The direct and intangible costs were of similar sizes, each contributing to approximately 40 % of total costs, whereas indirect costs contributed to approximately 20 %. The largest individual cost components were reduced quality of life among people who use drugs and costs of the criminal justice system. Conclusion: Illegal drug use has a negative impact on the societal aim to create good and equitable health in Sweden. The findings call for evidence-based prevention of drug use and treatment for those addicted. It is important to address the co-morbidity of mental ill-health and drug dependence, to develop low-threshold services and measures for early prevention among children and young adults, as well as to evaluate laws and regulations connected to illegal drug use.


Background
The use of illegal drugs, such as cannabis, cocaine, or ecstasy, is a wide-spread phenomenon (United Nations, 2021).Almost one third of people aged 15-64 in the European Union (EU) have used illegal drugs at some point in their lives (European Monitoring Centre for Drugs & Drug Addiction, 2022).In Sweden, 3.5 % of adults (aged 16-84) used illegal drugs during the past 12 months according to survey data from 2020, up from 2.5 % in 2014 (Public Health Agency of Sweden, 2022).The same survey data also showed that cannabis was the most common drug consumed.In 2020, Sweden and Ireland had the joint second highest number of drug-induced deaths per capita in Europe with 73 cases per million inhabitants among 15-64-year-olds, closely behind Norway with 85 cases per million inhabitants and far above the EU average of 17 cases per million inhabitants (European Monitoring Centre for Drugs & Drug Addiction, 2022).
Illegal drugs can have many negative effects for the people using them.This includes negative health effects, such as respiratory problems, cardiovascular diseases, mental health problems, and accidents (Devlin & Henry, 2008).Sharing of injecting equipment risks the transmission of blood-borne diseases such as hepatitis C (European Monitoring Centre for Drugs & Drug Addiction, 2021).Illegal drug use can also lead to death, either directly through an overdose or indirectly through drug-induced lethal diseases, accidents, violence, and suicide (OECD/European Union, 2020).Negative health effects can lead to work/school-related problems (Henkel, 2011).The vulnerable situation of people with problem drug use might cause a vicious circle that leads them to committing other crimes than drug-related crimes (Pierce et al., 2017).Defining the extent of all negative effects of illegal drug use is not easy as the direction of the causal relationship may run both ways (Degenhardt et al., 2014).
There are far-reaching economic implications of illegal drug use not only for people who use drugs (PWUD) but for the entire society.Various actors deal with and are affected by PWUD and the consequences of drug use.This covers health care and social care services that support PWUD and the criminal justice system that processes drug-related crimes.The police, schools, and different public authorities spend resources on preventive work.Unemployment and premature death by overdose result in a loss of resources to the society (the lost value of a potential worker).There is also a human cost of the physical and/or psychological strain on PWUD and their families (Birkeland et al., 2018;Melberg et al., 2011).
A review of studies on the societal costs of illegal drug use in countries of the EU published between 1990 and 2015 showed that the costs per capita ranged from €0.37 to €142 (Barrio et al., 2017).More recent estimates from Belgium and Spain indicated costs of €64 per capita and €30-35 per capita, respectively (Lievens et al., 2017;Rivera et al., 2017).An estimate for Canada for 2020 indicated much higher costs of €312 per capita (Canadian Substance Use Costs & Harms Scientific Working Group, 2023).A comparison of study results across countries is difficult because of methodological differences in the type of costs included, valuation of costs, and institutional differences in how countries tackle illegal drug use.
There is no up-to-date estimate of the societal costs of illegal drug use in Sweden or in similar settings that could be used as basis for future policy making.The most recent internationally published estimate for Sweden indicated costs of €950 million in 2002, equivalent to €114 per capita (adjusted to 2020 Euros for inflation and exchange rates), but only included some of the relevant direct costs (Ramstedt, 2006).The two most recent estimates published by the Ministry of Health and Social Affairs and the Public Health Agency of Sweden each indicated costs of approximately €271 per capita in 2008 (adjusted to 2020 Euros for inflation and exchange rates) (Ministry of Health & Social Affairs, 2011;Public Health Agency of Sweden, 2011).The latter reports also did not include all relevant types of costs and had to rely on many assumptions in the absence of detailed registry data.Access to registry data and other information on illegal drug use has improved significantly since then.The increasing use of illegal drugs in the Swedish population during the last decade also calls for a reassessment of the costs (Public Health Agency of Sweden 2022).Therefore, the aim of this study was to provide a comprehensive and up-to-date estimation of the societal costs of illegal drug use in Sweden, relying as much as possible on registry and administrative data rather than survey data.

Study design
A cost-of-illness (COI) study was conducted to estimate the societal costs of illegal drug use.A prevalence-based approach was applied.This entails the estimation of costs incurred during a given year (Byford et al., 2000).In this study, the reference year was 2020, which was the latest year with accessible information for most types of costs.A prevalence-based COI study requires the definition of a study population, the definition of the types of costs included and their valuation, and the calculation of costs including methods to address instances of unclear direction of causality.

Study population
In Sweden, illegal drugs are specified on an exhaustive list maintained by the Swedish Medical Products Agency (Swedish Medical Products Agency, 2022).This list includes psychoactive substances such as opioids, cannabinoids, amphetamines, cocaine, hallucinogens, solvents, and sedatives.
The prevalence of illegal drug use is regularly assessed by the Public Health Agency of Sweden through the national public health survey.According to survey data from 2020, 3.5 % of adults (aged 16-84) used illegal drugs during the past 12 months (Public Health Agency of Sweden, 2022), corresponding to around 286,000 people.Survey data generally underestimate the extent of illegal drug use due to respondents' unwillingness to disclose illegal activity (Johnson, 2014;Reuter et al., 2021).Therefore, this study used predominantly registry and administrative data to estimate component costs; see Table A1 in the Supplementary material.
In the various settings considered in this study, illegal drug use was defined in the following ways.PWUD accessing the health care system were identified in registry data through relevant codes of the International Classification of Diseases, 10th revision (ICD-10).People with a main diagnosis of ICD-10 codes F11-F16 and F18-19 were included.PWUD accessing social care and welfare services or in contact with the criminal justice system were identified through two legal terms, "illegal drugs" and/or "substance abuse" (a terminology in Swedish language corresponding to the previous DSM-IV term of "abuse", closely comparable to the ICD-10 diagnosis of "harmful use" still in use in clinical work in Sweden).The term substance abuse also includes alcohol, and assumptions were made about the proportion of people affected based on proportions observed in the health care system (ICD-10 F10 for alcohol vs. F11-F16 and F18-19 for illegal drugs).The number of PWUD experiencing negative effects on their quality of life as well as potentially seeking health care for mental health problems was limited to 29,500 "people with problem drug use", based on a previous registry-based analysis by the National Board of Health and Welfare (Public Health Agency of Sweden, 2010).
Survey data were only used in two settings.Data from the national public health survey were used to estimate labor market-related effects of people who reported having used illegal drugs in the previous 12 months.Data from a survey by the Swedish Council for Information on Alcohol and Other Drugs were used to estimate the number of people who were negatively impacted (e.g., felt strong anxiety, were physically harmed, had property destroyed) by the use of illegal drugs of "someone in their lives" (e.g., family member, ex-partner).This survey showed that 3.6 % of adults (aged 17-84), corresponding to around 290,000 people in 2020, stated that they had been negatively affected during the previous 12 months (Sundin et al., 2018).

Types of costs
A broad societal perspective was applied to define costs of illegal drug use.International and Swedish studies and reports on the costs of illegal drug use were reviewed to identify relevant types of costs (Barrio et al., 2017;Lievens et al., 2017;Ministry of Health & Social Affairs, 2011;Public Health Agency of Sweden, 2011;Ramstedt, 2006;Rivera et al., 2017).Swedish COI studies on alcohol consumption (Ramboll Management Consulting, 2019), smoking (Andersson et al., 2017), and problem gambling (Hofmarcher et al., 2020) were also reviewed to ensure that the included cost types reflect national circumstances.Table 1 lists all types of costs considered relevant for the estimation of the societal costs.
COI studies generally include three types of societal costs, direct, indirect, and intangible costs (Byford et al., 2000).All identified cost components were grouped according to these three types in Table 1.Direct costs included costs for health care services, social care and welfare services, the criminal justice system, employers, preventive work, research, and surveillance.These costs correspond to the value of societal resources used in relation to illegal drug use and its consequences (Guinness, 2011), and they were valued based on prevailing (market) prices.Private costs for the purchase of illegal drugs were not included (Vander Laenen et al., 2011).
Indirect costs represent the loss of societal resources due to impaired work capacity and premature death of working-age people caused by illegal drug use (Guinness, 2011).Costs refer here to the value of resources that are not being created due to reduced workplace productivity, sick leave and early retirement, unemployment, and premature mortality.In line with the human-capital method commonly used in COI studies (Hartunian et al., 1980), every potential work hour not spent working represents a loss.One hour of lost work corresponds to the value of the work that could have been carried out (Sculpher, 2001), defined in this study as the average gross salary plus social security contributions.Transfer payments within the social security system (such as sick pay or unemployment benefits) were not included to avoid double counting of costs.
Intangible costs represent the human costs of reduced quality of life from illegal drug use (Rice, 1967).In contrast to direct and indirect costs, they have no direct connection to the use or lack of creation of societal resources and are therefore sometimes excluded in COI studies.However, excluding intangible costs imposes the implicit assumption that the economic value of health-related quality of life is zero (Rice, 1967).In this study, quality of life was measured either in terms of quality-adjusted life years (QALY) and valued based on the most commonly cited value of a QALY used by Swedish health authorities (Svensson et al., 2015), or by a proxy cost based on the average compensation payment for crime victims in line with previous Swedish COI studies of alcohol consumption and problem gambling (Hofmarcher  Notes: n/a = not applicable.n.e.= not estimated.PWUD = people who use drugs.The level of uncertainty was graded on a four-point scalenegligible, low, medium, highaccording to the quality and nature of the underlying data as well as assumptions made in the estimation of the costs; see Table A2 in the Supplementary material for a more detailed description.The sum of the individual cost types does not sum up exactly due to rounding. T. Hofmarcher et al. et al., 2020;Ramboll Management Consulting, 2019).

Calculation of costs
A detailed description of the estimation of each cost component listed in Table 1 is provided in the Supplementary material.In short, the costs of each cost component were calculated by one of two methods depending on data availability; see Table A1 in the Supplementary material.The first method was a bottom-up approach in which costs were obtained by multiplying the number of affected people (i.e., the study population) with an average cost per person (so-called unit costs).The second method was a top-down approach, using data on aggregated costs of certain services or activities (so-called lump sum costs) and applying a proportion (%) assumed to be attributable to illegal drugs.Unit costs and lump sum costs were sourced from public reports by relevant authorities and organizations as well as from Statistics Sweden; see Table A1 in the Supplementary material.General statistics (e.g., population, inflation, earnings) were collected from Statistics Sweden.
A challenge in accurately estimating the size of each type of cost was the lack of information on causal relationships.Illegal drug use may be either the cause or the consequence of various life circumstances.Previous studies in related areas addressed this problem by discounting costs with a "causality adjustment factor".In line with a previous Swedish COI study on problem gambling (Hofmarcher et al., 2020), some cost components were either discounted with 50 % in cases where the direction of causality could plausibly run equally in both ways (such as for unemployment and mental health problems), or with 20 % in cases where there was more certainty (for debt management services); see Table A1 in the Supplementary material.
All costs were presented in euros (€) and 2020 prices.The average exchange rate in 2020 was 1 euro = 10.4848Swedish krona, and prices were adjusted to 2020 price levels using the national consumer price index when necessary.

Total costs
The analysis showed that the estimated societal costs of illegal drug use in Sweden amounted to €3.7 billion in 2020; see Table 1.These costs corresponded to €355 per capita and 0.78 % of the Swedish gross domestic product.
The direct and intangible costs were of similar sizes (€1.4 and €1.5 billion, respectively), each contributing to approximately 40 % of total costs, while indirect costs accounted for €0.8 billion and contributed to 21 % of total costs; see Fig. 1.The five largest individual cost components were intangible costs from reduced quality of life among PWUD (24 % of total costs), direct costs of the criminal justice system (18 %), intangible costs from reduced quality of life of family and friends (16 %), indirect costs from premature death (15 %), and direct costs of social care and welfare services (12 %).

Health care system
Health care costs of illegal drug use consist primarily of public costs of the 21 regional councils but also include patient co-payments for accessed services.The cost of health care related to illegal drugs amounted to €233 million, representing 17 % of direct costs.PWUD are taken care of by all levels of health care.Primary care only has a limited role in the early detection of illegal drug use, resulting in comparatively small costs.People requiring acute treatment due to overdose or psychosis are admitted to inpatient care.More severe cases with problem drug use can be confined to short-term compulsory care at special care institutions to receive treatment.Most of the long-term treatment is provided in specialized outpatient care for PWUD who have been discharged from special care institutions to prevent relapse.
The regional councils also run needle exchange programs to prevent the spread of blood-borne diseases.They also run dedicated centers for pharmacological treatment of opioid dependence which administer agents such as buprenorphine, methadone, and naloxone, and which is the biggest single cost component of all health care costs.Around a sixth of the health care costs consist of the treatment of health-related consequences of illegal drug use.This includes the treatment of infections with HIV and hepatitis B and C caused by unsterile drug injections.It also includes the treatment of mental health problems (such as depression and schizophrenia) and suicide attempts, both being considerably more prevalent among PWUD than among the general population.

Social care and welfare services
Social services run by the 290 municipalities have the responsibility to provide different types of care and welfare support to people with substance use disorder.The state also has a role in the financing of compulsory care imposed by the social services as well as in debt management.The cost of social care and welfare services related to illegal drug use amounted to €433 million, constituting 31 % of direct costs.
Most of these costs accrue from care of adults by the social services, which includes drug rehabilitation centers, and which should be provided on a voluntary basis.When people with substance use disorder oppose care even though care is deemed necessary, compulsory care at residential homes can be imposed.Children and young people are being taken care of by the social services in different types of homes, either because their parents were deemed unable to care for them due to substance use disorder or because they themselves have a substance use disorder and need a change of environment.The municipalities also offer debt counseling to PWUD with financial problems, and the Swedish Enforcement Authority is involved in cases when PWUD have become heavily indebted.The municipalities provide housing and shelter to PWUD who have become homeless, and they provide financial support to PWUD with financial problems.

Criminal justice system
In Sweden, the purchase and use of illegal drugs is illegal and penalized, and there are several types of crime directly and indirectly related to illegal drugs.For indirectly related crime, such as gang violence and gun violence, it was not possible to identify how many cases were unambiguously related to illegal drugs and the costs of such crime were therefore not included.Costs of crime directly related to illegal drugs (e.g., use and possession of drugs, drug-impaired driving, drug trafficking) amounted to €659 million, constituting 47 % of direct costs.These costs primarily covered crime investigations by the police and preventive work by the police, prosecutions in the general courts, and prisons and probation services.Work by the customs with drug seizures and investigations of drug trafficking represented a comparatively smaller part of the costs.

Employers
When a person must quit a job or is laid off due to the negative impact of illegal drug use on work performance, costs for the recruitment of a replacement arise for the employer.Employers in Sweden are also obliged to provide a good working environment, which includes occupational health care activities related to illegal drugs that are often carried out by external companies.The total cost of employers related to illegal drug use amounted to €48 million, constituting 3 % of direct costs.

Other direct costs
Several public authorities and non-governmental organizations are involved in preventive work with illegal drug use, other than the work by the police described above.Work by schools accounted for the biggest part of costs related to preventive work.Costs of conducting research at universities related to illegal drug use was comparatively small.Costs associated with the surveillance of existing and emerging illegal drugs by the Public Health Agency of Sweden could not be reliably estimated.
The included costs of preventive work and research amounted to €33 million, constituting 2 % of direct costs.

Indirect costs
Indirect costs could only be partly estimated.Productivity loss from drug-induced premature death (at a mean age of around 40 years) constituted 70 % of the included indirect costs.Productivity loss from unemployment and from work absence due to imprisonment were of similar sizes and accounted for the remaining included indirect costs.Survey data did not indicate any productivity loss from work absence due to sick leave and early retirement among PWUD, whereas productivity loss from reduced workplace productivity among PWUD could not be estimated due to insufficient information.

Intangible costs
Costs of the reduced quality of life among people with problem drug use as well as of the QALYs lost due to drug-induced death constituted 60 % of the included intangible costs.Reduced quality of life of family members, ex-partners, friends, co-workers caused by "someone in their lives" who uses illegal drugs constituted 40 % of the included intangible costs.The latter costs did not include the reduced quality of life of children and young people due to insufficient information.Crimes committed against third parties (i.e., a person without a relation to the perpetrator) under the influence of drugs or as a consequence of the perpetrators' drug use impair the quality of life of the victims, yet associated costs were not included in the estimations due to insufficient information.

Discussion
This study estimated the societal costs of illegal drug use to be €3.7 billion in Sweden in 2020, corresponding to €355 per capita.These results can be compared to previous national and international studies.From an international perspective, a review of studies in countries of the EU indicated costs ranging from €0.37 to €142 per capita (Barrio et al., 2017), and an estimate for Canada for 2020 yielded €312 per capita (Canadian Substance Use Costs & Harms Scientific Working Group, 2023), but none of the studies included intangible costs.When excluding intangible costs in this study, the per-capita costs amounted to €212 per capita.Thus, the costs estimated here exceeded previous estimates for EU countries (some of which seem outdated and incomplete) but are lower than in Canada.The higher costs compared to other EU countries might be explained by a more comprehensive inclusion of different types of costs, such as social care services and the criminal justice system, but also by the high reported number of drug-induced deaths in Sweden in a European context (European Monitoring Centre for Drugs & Drug Addiction, 2022).From a national perspective, the direct costs per capita of €135 estimated here for 2020 were of a similar magnitude as the direct costs of €114 estimated by a study for 2002 (after adjusting for inflation and exchange rates) (Ramstedt, 2006).The sum of direct and indirect costs of €212 per capita estimated here for 2020 was, however, lower than the approximately €271 estimated for 2008 (adjusted for inflation and exchange rates) by two government reports (Ministry of Health & Social Affairs, 2011;Public Health Agency of Sweden, 2011).This was partly driven by lower indirect costs in this study, as costs for work absence due to drug-related sick leave were set at zero, given that they could not be reliably estimated.
From a public health perspective, it is worthwhile to compare the costs of illegal drug use with costs of other public health issues of an addictive nature.Such a comparison may help to prioritize and weigh the costs and benefits of interventions by different stakeholders against each other.Considering only the subtotal of direct and indirect costs, the results from this study place illegal drug use with costs of €2.2 billion in third place in Sweden, behind alcohol consumption with €5.8 billion and smoking with €3.0 billion (Andersson et al., 2017;Ramboll Management Consulting, 2019), but ahead of problem gambling with €1.0 billion (Hofmarcher et al., 2020).Interestingly, the direct costs of illegal drug use contribute to a larger proportion (64 %) of the sum of direct and indirect costs than for alcohol consumption (42 %), smoking (38 %), and problem gambling (18 %).This is caused by relatively larger costs of the criminal justice system due to the illegal nature of illegal drug use.
The future development of the societal costs of illegal drug use in Sweden hinges upon several factors.One factor is the use of illegal drugs.If the increasing trend seen over the last decade continues, it will likely lead to increased future costs.
Another factor is the direction of future public efforts in relation to drug related problems.Current help-seeking behavior may be hampered by the perceived stigma of PWUD in the Swedish society (Holeksa, 2022;Soussan & Kjellgren, 2019), although a broad picture of potential barriers to treatment seeking in the whole drug-using population is lacking.
Recent regional examples of structured changes in the health care organization have demonstrated improved uptake of opioid maintenance treatment in Sweden (Andersson & Johnson, 2020;Braback et al., 2016).Improving the accessibility to treatment would in the short term likely increase the financial burden for the health care system, while in the long run, this may reduce costs related to chronic illness and lives lost.In addition, increased drug prevention efforts, such as early interventions for children and young people and counseling and support for adults, may increase costs for social services in the short term but decrease costs in the long run if the efforts are effective.
Another important aspect affecting the societal costs is the effectiveness of the laws and regulations related to drug use, both in relation to reducing drug use as well as to provide sufficient care and treatment to those in need.In the present study, crime-related costs could not be specified for specific substances, hence it is not possible to conclude which drugs cause the most costs.A report that the Public Health Agency of Sweden presented to the Swedish government in 2020 suggested a number of measures aimed to reduce both medical and societal harms from drugs, including an evaluation of the Swedish Penal Law on Illegal Drugs (Public Health Agency of Sweden, 2020).The suggested measures also include the development of low-threshold services, investigating the co-morbidity of mental ill-health, drug use and drug dependence as well as developing measures for early prevention among children and young adults.In 2022, the Swedish government initiated an inquiry with the aim to develop a drug policy that it is adapted to present and future challenges, ensuring that the drug policy is compatible with the requirements for evidence-based care, effective drug prevention and harm reduction.However, the inquiry should not evaluate and propose any legislative changes in relation to criminal law.
The costs presented in this study were calculated for the year 2020 which was affected by the start of the COVID-19 pandemic.Undoubtedly, the pandemic had an impact on the society in various ways, not least by reducing access to health care services during certain periods (Public Health Agency of Sweden, 2021).However, comparing the years 2019 and 2020, official statistics by the National Board of Health and Welfare for specialized outpatient care, inpatient care, and compulsory care indicated no clear reductions of care episodes related to illegal drugs (National Board of Health and Welfare.2021).The same was true for the number of drug-induced deaths reported by the Public Health Agency of Sweden.Moreover, drug-related crimes exhibited a small increase (Swedish National Council for Crime Prevention 2021).
The cost estimations in this study include several uncertainties.The direction of causality between socioeconomic circumstances, such as mental health problems and unemployment, and illegal drug use needs to be better understood and quantified.This study addressed this by discounting the estimated costs with a causality adjustment factor in line with previous COI studies in related areas.The exact size of this factor was based on previous studies but remains somewhat arbitrary.
Some costs of social care and welfare services were imprecisely estimated because available information only refers to costs of substance abuse, which also includes alcohol.To overcome this problem, we applied an adjustment factor based on the proportion of care episodes related to alcohol compared to illegal drugs observed in the health care system, implicitly assuming that this proportion is similar for social care and welfare services.
Costs of the criminal justice system only included crime directly related to illegal drugs, i.e., drug crimes such as private use and possession, drug-impaired driving, and drug trafficking.Yet drug trafficking is also part of serious and organized crime which leads to gang violence and gun violence because of conflicts and competition within the drug market (Europol, 2021).The costs of these drug-related violent crimes were not included.The costs of crime committed by PWUD to get money to purchase drugs were neither included.
The use of survey data in the estimations was limited to a few circumstances where no other official data was available.Survey data are not optimal since the respondents may hesitate to reveal illegal actions (Johnson, 2014).The estimates of the direct costs related to employers and the indirect costs related to unemployment are thus more uncertain.
The number of people with problem drug use (29,500) was used in the estimations of the quality of life of PWUD and the number of PWUD who potentially seek health care for mental health problems.This estimate is based on registry data from 2007, and the real number of people with problem drug use has probably increased since then, which contributes to an underestimation of current costs.
The estimation of the intangible costs includes several uncertainties.They include the size of the reduction in quality of life among PWUD, which was based on an estimate by the World Health Organization in the absence of Swedish data, and the number of people affected, as only those with problem drug use were included.The valuation of reduced quality of life in monetary terms is also somewhat arbitrary but based on methods applied in previous studies.Some societal costs could not be included due to lack of data.This included the work by certain non-governmental organization, the work of public authorities involved in the surveillance of existing and emerging illegal drugs, productivity loss from reduced workplace productivity and from sick leave and early retirement of PWUD, and reduced quality of life of crime victims in no close relation to PWUD.The exclusion of these costs leads to an underestimation of the true societal costs in this study, but as to our understanding, nearly all measurable and potentially major cost components have been included in the estimations.
Given the various levels of uncertainty and assumptions required, some COI studies of illegal drug use provide ranges of costs rather than point estimates as in this study.Here we chose to provide a subjective assessment of the level of uncertainty (negligible, low, medium, high) of all point estimates shown in Table 1; see also Table A2 in the Supplementary material for a more detailed description.The uncertainty level of the five largest individual cost components differs as follows.Intangible costs from reduced quality of life among PWUD have high uncertainty for the part not relating to drug-induced deaths due to the size of the affected population and their size of reduction in quality of life as well as the method of valuation, direct costs of the criminal justice system have low uncertainty due to the use of administrative data, intangible costs from reduced quality of life of family and friends have high uncertainty due to the use of survey data and the method of valuation, indirect costs from premature death have low uncertainty, due to the use of registry data, and direct costs of social care and welfare services have medium uncertainty due to several assumptions about the proportion of placements at residential care homes and foster homes for children and young adults as well as voluntary care for adults.
A limitation of this study is the joint consideration of illegal drugs rather than an analysis of various substances.Some types of costs arise only from specific substance use disorders, e.g., maintenance treatment using opioids as substitution for the primary drug of people who use them are exclusive to opioid dependence and may vary little with changes for example in cannabis use in the society.Likewise, injectionrelated consequences are associated with specific drugs, in particular amphetamines and certain opioids, whereas again they vary little with an increase or decrease in the use of non-injectable drugs.In the present analysis, illegal drug use was considered as one entity, allowing for direct comparisons with other health hazards, whereas the data do not allow for detailed substance-specific conclusions to be drawn.Future analysis could explore more disaggregated data by substance, e.g., to support substance-specific policy evaluations of changes in the legal status.

Conclusions
Illegal drug use is an important public health concern in Sweden.
This study found that the associated societal costs amounted to €3.7 billion in 2020, corresponding to around €355 per inhabitant.These costs were high compared to results from other European countries.This large financial burden to society calls for effective preventive interventions, the use of evidence-based methods in the treatment of drug use disorders as well as the follow-up of these measures.In addition, given the large costs of the criminal justice system related to drugs, an evaluation of the current laws and regulations connected to illegal drug use should be considered.It is also particularly important to address the co-morbidity of mental ill-health, drug use and drug dependence as well as to develop low-threshold services and measures for early prevention among children and young adults.Ultimately, societal action against illegal drug use and the associated costs is crucial for reaching the overarching goal of the Swedish public health policy, which is to create societal conditions for good and equal health in the whole population.

Declaration of Competing Interest
TH has no conflict of interest to declare.AL, AM, JS are employed at the Public Health Agency of Sweden, which assigned and partly funded the study, but none of them were involved in the choice of methods in this study.AH has an overall research funding from the state-owned gambling operator of Sweden, AB Svenska Spel, and he also has project-specific funding from the research council of Svenska Spel and from the research council of the Swedish alcohol monopoly Systembolaget, but none of these organizations have had any involvement in the present study.

Fig. 1 .
Fig. 1.Estimated societal costs of drug use in Sweden in 2020.

Table 1
Estimated societal costs of illegal drug use by type of cost in Sweden in 2020.