There's no evidence in scientific articles that show aphantasia is caused by psychological trauma. But most of "caused" aphantasia starts after damage to a specific part in the left temporal lobe.
Some articles that I've read (but please take it with a bit of salt, as it has already been said, there are not enough research in the area and I'm not an specialist, just someone who was curious about):
the architect who lost his ability to imagine: the cerebral basis of visual imagination
selective deficit of mental visual imagery with intact primary visual cortex and visual perception