Others claim that veneration of the crucifix - rather than simply an ornate flat cross - was introduced in the medieval period, and this was blessed by the grace of stigmata appearing. The appearance of the crucifix has been controversial in Christianity, and some staunch traditionalists believe that stigmata is a divine sign of approval for this devotion. (One hardly need add the rationalist critique of this, which is that the visual aid is causing imitation.)
A recent article on americancatholic.org takes a moderate position. It says:
Q: Recently, after watching a video about the life of Padre Pio, my husband and I wondered why the wounds appeared in the hands rather than the wrists. The hand sites are found depicted in many traditional paintings, while the wrists are the accepted actual site of the piercing. Could this anomaly be proof of a less-than-miraculous reason for the stigmata?
A: Two reference books shed light on your question. The HarperCollins Encyclopedia of Catholicism, edited by Richard P. McBrien, states, "On very rare occasions the Catholic Church has accepted an occurrence of the stigmata as authentic, but has never defined their origin or nature, thus allowing physical, psychological and preternatural explanations for these phenomena."
Ian Wilson, in Stigmata (Harper & Row, San Francisco), declares, "They [stigmata] are one of the most baffling and intriguing of medical and scientific mysteries."
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?
As I read Wilson, he searches for a natural explanation of the stigmata. 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.
For books on the stigmata besides Wilson’s, see: Voices, Visions and Apparitions and They Bore the Wounds of Christ: The Mystery of the Sacred Stigmata, both by Michael Freeze, S.F.O. (Our Sunday Visitor).
Interesting thought.