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Analyzing the drug abuse epidemic There is a developing drug epidemic in the United States. Jalal et al. analyzed nearly 600,000 unintentional drug overdoses over a 38-year period. Although the overall mortality rate closely followed an exponential growth curve, the pattern itself is a composite of several underlying subepidemics of different drugs. Geographic hotspots have developed over time, as well as drug-specific demographic differences. Science, this issue p. eaau1184 The drug overdose epidemic in the United States is a composite of drug-specific subepidemics. INTRODUCTION The epidemic of substance use disorders and drug overdose deaths is a growing public health crisis in the United States. Every day, 174 people die from drug overdoses. Currently, opioids (including prescription opioids, heroin, and synthetic opioids such as fentanyl and its chemical analogs) are the leading cause of overdose deaths. The overdose mortality data can reveal the complex and evolving dynamics of drug use in the United States. RATIONALE Reports on the U.S. drug overdose epidemic tend to focus on changes in yearly statistics. Improved understanding of the long-term dynamics of the overdose epidemic may aid in the development of more effective epidemic prevention and control strategies. At present, there are no reliable methods to forecast the likely future course of the epidemic. We focused on deaths from overdoses as a relatively reliable metric of the epidemic because all deaths are required to be reported in all U.S. states and territories using the standardized International Classification of Diseases. In an effort to understand the epidemic dynamics and perhaps predict its future course, we analyzed records of 599,255 deaths from 1979 through 2016 from the National Vital Statistics System where unintentional drug poisoning was identified as the main cause of death. We examined the time course of the overall number of deaths; the contributions of individual drugs (prescription opioids, heroin, synthetic opioids like fentanyl, methadone, cocaine, methamphetamine) to the overall curve; changes in the populations most affected by each drug as measured by demographic factors of age, sex, race, and urbanicity; and changes in the geographic distribution of deaths due to each drug as measured by the county of residence of each decedent. RESULTS The overall mortality rate for unintentional drug poisonings in the United States grew exponentially from 1979 through 2016. This exponentially increasing mortality rate has tracked along a remarkably smooth trajectory (log linear R2 = 0.99) for at least 38 years (left panel). By contrast, the trajectories of mortality rates from individual drugs have not tracked along exponential trajectories. Cocaine was a leading cause in 2005–2006, which was overtaken successively by prescription opioids, then heroin, and then synthetic opioids such as fentanyl. The demographic patterns of deaths due to each drug have also shown substantial variability over time. Until 2010, most deaths were in 40- to 50-year-old persons, from cocaine and increasingly from prescription drugs. Deaths from heroin and then fentanyl have subsequently predominated, affecting younger persons, ages 20 to 40 (middle panel). Mortality rates for males have exceeded those for females for all drugs. Rates for whites exceeded those for blacks for all opioids, but rates were much greater among blacks for cocaine. Death rates for prescription drugs were greater for rural than urban populations. The geographic patterns of deaths also vary by drug. Prescription opioid deaths are widespread across the United States (right panel), whereas heroin and fentanyl deaths are predominantly located in the northeastern United States and methamphetamine deaths in the southwestern United States. Cocaine deaths tend to be associated with urban centers. The online manuscript provides many details of the patterns of mortality in these data. CONCLUSION The U.S. drug overdose epidemic has been inexorably tracking along an exponential growth curve since at least 1979. Although there have been transient periods of minor acceleration or deceleration, the overall drug overdose mortality rate has regularly returned to the exponential growth curve. This historical pattern of predictable growth for at least 38 years suggests that the current opioid epidemic may be a more recent manifestation of an ongoing longer-term process. This process may continue along this path for several more years into the future. Paradoxically, there has been substantial variability with which specific drugs have become dominant in varying populations and geographic locales. This variability all but negates the possibility of confident predictions about the future role of specific drugs. Indeed, it is possible that a future overdose epidemic may be driven by a new or obscure drug that is not among the leading causes of drug overdose death today. Understanding the forces that are holding multiple subepidemics together onto a smooth exponential trajectory may be important in revealing, and effectively dealing with, the root causes of the epidemic. Exponential growth in overdose deaths. The smooth overall U.S. overdose mortality curve (left panel) is a composite of multiple subepidemics, as revealed by changing patterns of overdose deaths by age distribution (middle panel; color indicates deaths per 100,000 persons), and by geography (right panel; color shows hotspots), for prescription opioids (upper) and heroin (lower). Subepidemic patterns for other drugs are shown in the full manuscript. Better understanding of the dynamics of the current U.S. overdose epidemic may aid in the development of more effective prevention and control strategies. We analyzed records of 599,255 deaths from 1979 through 2016 from the National Vital Statistics System in which accidental drug poisoning was identified as the main cause of death. By examining all available data on accidental poisoning deaths back to 1979 and showing that the overall 38-year curve is exponential, we provide evidence that the current wave of opioid overdose deaths (due to prescription opioids, heroin, and fentanyl) may just be the latest manifestation of a more fundamental longer-term process. The 38+ year smooth exponential curve of total U.S. annual accidental drug poisoning deaths is a composite of multiple distinctive subepidemics of different drugs (primarily prescription opioids, heroin, methadone, synthetic opioids, cocaine, and methamphetamine), each with its own specific demographic and geographic characteristics.