Mercury gets dtk bala, or directional strength, in the 1st house. Therefore this is its best position. However, consideration of aspects is crucial, since Mercury is adaptable and becomes a malefic if in the presence of other malefics. With Mercury in the 1st, the person is youthful in appearance. He will be intelligent, learned, and knowledgeable. He may be a writer or take up any career relating to communications. He will be witty and ingenius. He is an excellent speaker and will be very talkative. There will be talent or interest in math, poetry, fine arts, or astrology. The person is handsome, respected, healthy, and long-lived. Married life is happy and comes at an early age. The person will be skilled in languages. He will be happy, friendly, and charming. He will also be kindhearted and forgiving. He may be a twin, as this is one of the most common indications of such. If Mercury is afflicted, the person will be nervous, excitable, and mentally unstable. He will be conceited, constantly bragging, and lacking in real confidence.

UCHCHA and SWAKSHETRA (exalted and own sign). If Mercury is in Virgo or Gemini in the ascendant, there will be great intelligence, and the benefits listed above are heightened. The person will be beautiful, and will enjoy honor or fame. He will be virtuous, fortunate, and wealthy. He will have been born to a wealthy or refined family.

NEECHA (fallen). If Mercury is in Pisces in the 1st, there will be no confidence or self-respect. The person is nervous, excitable, mentally unstable, or of a wavering mind. There will be a struggle for self-acceptance throughout life. The person will be poor, unfortunate, weak, and unhealthy. Longevity is decreased and married life suffers.

Mercury gives its full effects in the 32nd year, and at that time, there will be benefits regarding 1st house affairs unless the planet is afflicted or evil due to the houses it rules.

Source: «Ancient Hindu Astrology for the Modern Western Astrologer» by James Braha