For a native to have sound constitution and robust health the lagna and its lord should be strong and the lord of 6th should be weak. Sun is a natural atamkaraka and gives health and energy. i e should be strong and free from malefic influence (especially from Saturn or Rahu) to give good health. Moon the planet of mind should also be frees from afflict ion for a clear and sound thinking.
Those who have little knowledge of astrology are aware that 6th. 8th and 12th houses are dusthanas. Malefics in these places are not good for health. 6th house is of diseases and the 6th lord does give ill-health during its dasabhukti. In the chart look for the planet in the sixth from lagna and Moon, lord of the 6th house and the sign containing the 6th house. These all combined together will give a clue about the disease and the part of the body affected by that disease. Besides these three trik houses, even the other houses if badly afflicted and containing planets badly afflicted give specific diseases governed by those houses, signs and the planets contained in them. Such diseases are normally experienced during their dasabhukti of the afflicting planet(s) having sambandha with such a planet. The gochara of an afflicted planet is causative of a disease since a disease is caused when a planet is in an un-favorable position in gochara and its dasabhukti is running
Example, an affliction to first house in a chart and Aries impairs the brain and nervous system causing various diseases from headache to insanity and accidents involving the head and brain. An affliction to sign Cancer and the 4th house will cause mental diseases like lunacy, retardation, dullness and also emotional diseases like fits, epilepsy, phobias and coma etc. An affliction to 5th house results in aberration of mind, schizophrenia. paranoia and perversion etc.
If the lagnesh is in 6th, the 8th or the 12th, especially the 6th, it is an indication that the native will be sickly. The matter becomes worse if lagnesh is aspect by a malefic whereas the aspect of a benefic gives a boost for good health. Malefics in dusthanas are not good for health.
The dasa of a planet in the 2nd or the 7th (maraka houses) from lagna or chandralagna can also bring ill health. Jupiter in the 6th or aspecting the 6th gives good health. Jupiter with Moon or in the 5th house or aspecting the Moon or the 5th house is good for mental health. If the lord of 9th aspects the 6th and the 8th house there will be good health. Moon with Saturn causes a weak physique, a worried mind, poverty and liability to false charges unless Saturn is the lord of lagna or is well aspect by Jupiter. Moon with Rahu or Kethu, especially Rahu, is not good for general health or mental balance. New Moon, being a malefic, is good in 3rd, 6th and the 11th house.
6th house represents the house of diseases. Saturn or Rahu in this house though good for prosperity, causes illnesses. If the 6th house is Virgo, disease is of the stomach or bad digestive power on account of poor secretion of gastric juices or diarrhoea or dysentery. I may add that 6th house denotes diseases. 8th house denotes long illness that may be fatal in character, whereas, 12th house indicates confinement in a hospital. Venus in 6th (except, perhaps, when in Libra or in an adhi yoga configuration) is bad to cause venereal diseases especially if it is afflicted by Saturn or Mars or any node. Moon is a watery planet and if conjoined with or aspect by fiery Mars, it may cause instability of mind and may make the native violent in mind, furious, abusive, malicious and treacherous. Saturn's affliction to Moon makes one gloomy and melancholic and native becomes dull, impertinent and obstinate. If this affliction occurs in a good house then the native becomes serious and has good patience in carrying out research activities. Mercury governs one's intelligence and thinking. If it is afflicted, especially by its enemy, Mars his thinking is badly affected and the native is likely to fly in fury occasionally and use incoherent language.