We remember the year 2000 as a boom time for the US economy (my first teaching job interview lasted around five minutes), but lots of bad things spike when the economy is good, too. Take, for example, pedestrian deaths from getting hit by cars:
It looks to me like pedestrian deaths took a tumble when the economy did, but have come roaring back even stronger, perhaps because of distracted drivers and distracted pedestrians.
By analogy, I tend to be skeptical of claims that increasing drug deaths are a straightforward result of economic despair. Lots of things get worse when the economy is humming along faster.