The cause of vaginismus is not fully understood but is often developed due to the association of vaginal pain following yeast or bladder infection, whilst for some women it can be a fear of potential pregnancy. Painful penetration usually triggered by unpleasant sexual experience. It can be related to sexual abuse, at times it is experience in doctors office and other times the cause is very strict religious upbringing.
The aftermath of a painful experience causes the brain to send a signal to the vaginal muscle to contract, which causes more pain on penetration, setting a vicious cycle into play. Even when the original cause of pain is no longer a present factor, the contraction of the vaginal muscle on penetration occurs automatically.