Interesting caution about self-selection bias in a post-abortion study

https://www.washingtonpost.com/health/2020/01/12/five-years-after-an-abortion-most-women-say-they-made-right-decision/

"In a 2018 paper in Linacre Quarterly, the ethics journal of the Catholic Medical Association, antiabortion activist David C. Reardon describes how more than two-thirds of the women approached for the study refused to participate. Of those who agreed, half dropped out. Those who reported the highest rates of relief and happiness were the ones most likely to remain, he argued. Those who reported the least relief were most likely to drop out, he said."