In that paper, the authors conclude:
> 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. By contrast, the trajectories of mortality rates from individual drugs have not tracked along exponential trajectories.
The authors also suggest that we should attempt to "understand the forces that are holding multiple subepidemics together onto a smooth exponential trajectory", and suggest a double-whammy of increased supply (due to improved communication, transportation, and manufacture) and increase demand (despair, loss of purpose, and dissolution of communities) that cuts across both demographics and geographic regions.
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