Researchers do not have an exact answer to this question. Perhaps vascular spasm develops due to an imbalance of factors responsible for vasoconstriction (vasoconstrictors) and substances responsible for their expansion (vasodilators).
updates
Researchers do not have an exact answer to this question. Perhaps vascular spasm develops due to an imbalance of factors responsible for vasoconstriction (vasoconstrictors) and substances responsible for their expansion (vasodilators).