What is the ruling on the prayer of a person afflicted with obsessive-compulsive disorder (waswas) who repeats prostration more than once? Does this invalidate his prayer? Is this considered to be in line with the view of Ibn Qudamah in condemning those afflicted with waswas?

The effects of waswasah (whispers/obsessive thoughts) include repeating an act, believing it wasn't completed, and this can reach a point of overwhelming the intellect. The person afflicted with waswasah is required not to pay attention to doubt. His prayer is valid if he repeats prostration under the influence of waswasah, believing he didn't perform it, and he is not required to perform the prostration of forgetfulness (sujood as-sahw) if the doubt recurs daily. However, if he intentionally adds a rukn (pillar), his prayer is invalid. The best cure for waswasah is to ignore it.