Yogas or special planetary combinations or configurations occupy a very important place in Vedic Astrology. Yogas are either benefic or malefic.

Results yogas produce 
The presence of benefic or favourable Yogas in a horoscope enhances the stature and the personality of a person while conferring specific benefits such as fame, wealth, high status, eminence, robust health, longevity and invincibility. Malefic Yogas cause early death, ill-health, physical and mental defects, poverty, disrepute, misery and suffering. 

How Neecha Bhanga Rajayoga is formed
Neecha Bhanga Rajayoga is one of the prominent benefic yogas much discussed in classical Indian works on Astrology. 

According to ancient Indian sages, Neecha Bhanga Yoga confers very high status and great fortune on the native. 

The term Neecha in Astrological parlance is used in reference to the status of a planet. Neecha means ‘debilitated’.  The opposite of being Neecha is being ‘Uchcha’ which means exalted.  Planets attain exaltation when posited in certain signs or Rashis and debilitation in certain other Rashis. For examples, Sun becomes Uchcha or exalted in Aries (Mesha) and Neecha or debilitated in Libra (Thula). Moon is Uchcha in the first three degrees in Taurus and Neecha in Scorpio.  The other planets become either Uchcha or Neecha when placed in the 12 signs in the Zodiac as shown below.

Most Indian astrologers consider Rahu gets Neecha in Sagittarius and Ketuin Gemini.

Neecha Dosha
It should be noted that a planet gets debilitation in the 7th House or 180 degrees from the sign of its exaltation. 
Students are advised not to consider a horoscope is weak because one or more planets are debilitated in it. They have to look for planetary combinations that can nullify the Neecha Dosha like the Neecha Bhanga Yoga before making judgments.

Mercury and the 9th House 
Normally debilitation of Mercury and the presence of a debilitated planet in the 9th House are considered very unfavourable. The rationale for this rule is that Mercury is the planet which confers intellect and intelligence and a debilitated Mercury cannot endow a native with these qualities so essential for a normal human being.  As for the 9th House -  this House is considered the House of fortune or good luck.  One cannot be expected to be fortunate or lucky if the Bhagyasthana is afflicted.    

In certain instances, debilitated planets confer benefits to the native even if there are no combinations that can give rise to Neecha Bhanga Rajayoga. 

Benefits resulting from Neecha Dosha
It is the general opinion among competent astrologers that some planets like the Sun, Saturn and Jupiter become more beneficial for the native in terms of material success when debilitated than when exalted.

For example, a debilitated Sun makes the native humble, simple, frugal-minded and persevering, qualities which would make his life a success. 

However, a debilitated Sun is considered bad for kings and rulers who are expected to exercise power and authority. A debilitated Saturn too is considered favourable in material terms as he would confer wealth on the native. A debilitated Jupiter too becomes favourable because the native would strive for worldly success.  

Combinations that nullify Neecha Dosha            

• Neecha Dosha of debilitated planets get cancelled or nullified in the following ways: 
• When the debilitated planet is associated with or aspected by its exaltation sign’s lord
• When two debilitated planets aspecteach other
• When the debilitated planet is associated with or is aspected by   its debilitation sign’s lord
• When the lord of the House where he gets exalted is in a Kendra from the Lagna or the Moon.
• When the lord of the House where he gets debilitated is in a Kendra from the Lagna or the Moon.
• When the debilitated planet exchanges Houses with its debilitation sign’s lord 
• When the debilitated planet is endowed with good Ashtakavarga strength
• When the Navamsa of the debilitated planet occupies a Kendra or a trine from the Moon and the Moon and the Lagna happen to be movable signs or Lagna Navamsa happens to be a movable sign.