Actually the 9th house, which is the house of Spirituality. A major affliction on the 9th house indicate a person being an atheist. 9th house is also the natural house of Jupiter and Jupiter is the planet of belief. Atheist is also a belief that they do not believe in anything as God. Therefore affliction on Jupiter and the 9th house , say of Rahu, can make a person an atheist.
Blessings,
Navneet Khanna
Astrologer