Obviously, there are few sure answers we can give or find regarding the stigmata. We are not even certain how the stigmata (wounds of the Passion)looked on Christ’s body. We can only speculate. But we do know that the stigmata do not appear the same in all who are believed to have had them.
One stigmatic, for instance, had only the wounds that would have been made by the crown of thorns. Two possessed only the wound in the side. Some had the lance wound in the left side (Padre Pio), another in the right side (St. Francis of Assisi). One had the hand wounds in the wrists, others in the palms of the hands.
Is it significant that more women than men have had the stigmata? What can we conclude from the fact that most stigmatics came from the Dominican and Franciscan Orders? And what does it say that some saints were stigmatics but not all stigmatics were saints?
Ian Wilson, in Stigmata, searches for a natural explanation. Among the possibilities he suggests is some inner mechanism comparable to that which under stress produces evolutionary adaptations in species.
In his study, Wilson notes some stigmatics seem to have identified with earlier stigmatics—ultimately with Jesus. Finally, Wilson notes, "A really riveting feature is the extraordinary precision of the mechanism’s conformity to the visualization that triggered it. Stigmata have been precisely positioned to conform with the wounds of a stigmatic’s favorite crucifix. Or a wound may have taken on the exact shape, such as a cross."
That seems to imply that the stigmata may occur according to the way the subject pictures or imagines them.