Must one make up prayers missed over two years due to obsessive-compulsive disorder, and is expiation required of him?

Abandoning prayer is not a solution; rather, it is a Muslim's aid, and Allah has commanded us to seek help through it. Making up missed prayers is obligatory according to the majority of scholars, and it is an expiation for abandoning them, based on the hadith: "Whoever sleeps through a prayer or forgets it, let him pray it when he remembers it, for there is no expiation for it except that." As for whisperings (waswas), their cure is to ignore them and to occupy one's time with seeking knowledge, listening to the Quran, exercising, and reading about the lives of the Pious Predecessors (Salaf).