Mental illness in astrology
In vedic astrology, we look 1st and 7th house and if Saturn and mars mutually aspect each other. If moon is completely eclipsed by Sun, then mental illness can be a factor.
medical astrology
How planets cause illness
Any malefics, sun, mars, rahu, ketu, saturn in fifth or eleventh house causes stomach problem.
Sun is for vision, sun in second house causes right eye problem and in twelfth house causes left eye problem, if aspected by malefic like Mars, rahu, saturn, it can cause severe eye problem.
Diseases caused by planets in Vedic astrology
The trik, dustana or evil houses (6th,8th,12th) and planets related to the house plays an important role in deciding the health of the native. Sixth house decides the lower abdomen problem, Eighth house represents chronic diseases and twelfth house represents hospitalization.