I found a very old question here - Mediator reverses direction of causal variable. How to interpret?, but it isn't answered. I am having almost the same issue as @jsd. I've run mediation following Baron and Kenny and confirmed it with the Sobel test. Here's what I get when I run the regressions (all variables are continuous):

  • X significantly negatively predicts Y
  • X significantly negatively predicts M
  • M significantly positively predicts Y
  • X + M significantly positively predict Y
  • In the last model with both X and M, M no longer significantly predicts Y.

I checked moderation since the relationship reversed. There is no moderation. X and M do not significantly interact.

This post (Mediation (b path sign changes from the correlation)) suggests it is mediation, but that it is suppression. I looked at suppression, but if I'm understanding it right, X and M are not supposed to have a relationship in suppression. So, do I have mediation? Or suppression? Or something else?

Thank you in advance for any help!


1 Answer 1


I think I just figured it out. I have inconsistent mediation - Equivalence of the mediation, confounding and suppression effect MacKinnon et al., 2000 found here: http://europepmc.org/article/PMC/2819361


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