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Sexual perversion is outcome of affliction on various planets governing various factors.   A person  (ascendant) will be perverted if his emotional aspect (Moon 5H/L) is under affliction to create excessive lust for lascivious pleasures (Venus, 7H/L, 8H/L, 12H/L) secretly (12 H/L). He / she will have extra courage (Mars, 3L, 3H) also to break the socially accepted norms (Rahu, affliction on 5H/L and involvement of 8H/L) for sexual act (7H/L) in multiplicity (11H/L).  Besides, there would be noticeable degradation in character of such person (affliction on Sun and influence on Saturn on above factors).  These factors form various combinations that may show sexual immorality of native.  A few combinations are as follows:

Mars link with 7H/L and Venus.

Mars in Venus sign but in Saturn or Mars Navamsha and Venus in Mars sign but in Saturn or Venus Navamsha.
Venus in Aries, Taurus or Aquarius aspected by Mars.
Conjunction of Mars and afflicted Venus.
Venus in Vargas of Mars and Saturn.
Venus in 7th house aspected by Mars or Saturn Rahu etc.
Venus in Virgo or Cancer aspected by Saturn.
7L with R/K aspected by malefic.

Rahu in 7H and Mars in 4H.

Venus in Gemini or Virgo aspected by Mars. Mercury and Venus seek secret pleasure.
Strong Sambandha between lords of 7 and 11H.
Exchange between 7L and 12L.
Mars Mercury Venus in 7H makes one extremely passionate.  Venus in Aries makes one mentally passionate, in Scorpio physically passionate.
Saturn aspected by or associated with Venus in Mars sign.
Saturn Mars Moon  in 7th House.
Mars in 4H, Rahu in 7H and Sun & Saturn together in any sign.
Rahu or Sun in 7H and Mars in 4H or 7H.
LL, 2L or 6L in 7H with malefic.
Jupiter, Mercury or Venus Moon or Sun Rahu or Saturn Rahu or Saturn Ketu in 7H.
All Kendras are afflicted or Malefics in trines.

Saturn, Sun, Mars in 4H.