The development of the ‘Forms of Responding to Self-Critical Thoughts Scale’ (FoReST)

•Self-critical thoughts are associated with a range of mental health difficulties.•High levels of psychological inflexibility are associated with increased distress.•A measure of psychological inflexibility related to self-critical thoughts is needed.•The factor structure and validity of a new measure called the FoReST are explored.•The FoReST is a valid measure of inflexible responding to self-critical thoughts.