The exponential growth in overall mortality from unintentional drug overdoses in recent decades is a composite of multiple underlying sub-epidemics of different drug types, each with its own unique set of social and geographic characteristics, reports a new study. The findings suggest that understanding these nuanced dynamics could aid the development of more effective prevention and control strategies. In the United States, opioids, which include prescription painkillers and fentanyl, are the main cause of drug overdose deaths, leading U.S. officials to declare the opioid crisis a public health emergency. However, opioids are merely a recent part of a larger epidemic of drug overdose deaths, which have been steadily on the rise for decades. To better analyze the growing drug epidemic in the United States, Hawre Jalal and colleagues analyzed the mortality patterns of nearly 600,000 unintentional drug overdoses over a 38-year period (1979-2016). The results show that none of the mortality curves from individual drugs demonstrate any regular or predictable pattern. However, when the annual sum of overdose deaths is combined, the overall mortality rate forms a smooth exponential growth curve. To illuminate mortality patterns as driven by demography and geography, the authors created novel data visualizations using heatmaps and geospatial hot-spot analyses. One finding suggests that almost every region in the country is a hotspot from at least one type of drug, except for select areas in the north central U.S. Jalal et al. note that understanding the mechanisms that explain how multiple distinct and variable mortality rates merge to create an overall exponential trajectory could be important in revealing the root causes of the epidemic.