Pennebaker's experiments, begun over twenty years ago, have been widely replicated and validated. Following on from Pennebaker's original work, there has been a renewed interest in the therapeutic value of abreaction. This was first discussed by Josef Breuer and Freud in "Studies on Hysteria" but not much explored since. At the heart of Pennebaker's theory is the idea that actively inhibiting thoughts and feelings about traumatic events requires effort, serves as a cumulative stressor on the body, and is associated with increased physiological activity, obsessive thinking or ruminating about the event, and longer-term disease. However, as Baikie and Wilhelm note, the theory has intuitive appeal but mixed empirical support: