<Figure 2. Piecewise linear regression of the
sign and attribution time-series for citing papers published from
1986-2019 >
For affirmational and neutral citations, a breakpoint was identified in
1996, after which the rate decreased significantly (Figure 2a).
Non-attributive citations also had a breakpoint in 1996 (Figure 2b).
The time-series analysis for negational citations identified a
significant breakpoint in 2004 (Figure 2a). Following that year, the
number of negational citations substantially increased. Similarly, the
time-series analysis for citations that attribute the opioid crisis to
Portenoy’s paper had a distinctive breakpoint in 2004 (Figure 2b). After
2004, many more papers cited Portenoy’s paper as a motivating factor
behind the opioid crisis.