A patient describes his mind suddenly going blank mid-sentence, with no thought there at all where a moment before there had been one — but when asked what caused it, he simply says he doesn't know, it just happened, with no sense of anyone or anything taking it from him. Before revealing the answer: is this thought withdrawal?
No, this is more consistent with thought blocking than with thought withdrawal. Both present as a sudden gap in thinking, but thought withdrawal specifically carries an explicit sense of active external removal, whereas here the patient describes only an unexplained blank with no felt external agent responsible. The presence or absence of that felt external cause is exactly what separates the two, and here it is absent.
References
- Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 4, 'Disorders of Thought and Speech'.