Psychic bond
A psychic bond was a long held belief among Vulcans that thoughts, feelings, and images could be shared with another after they mated. 

In December 2154, T'Pol told Charles Tucker III that, as a result of their becoming intimate a year previously, they shared a psychic bond which explained why they saw each other in daydreams they had. The bond also made Tucker immune to the effects of Orion slave girls  was carrying on board at the time due to T'Pol's Vulcan physiology. ()

Vulcan
Mythology
Medical conditions