Best free place to find actual studies is the US National Institutes of Health medical library. It's called
PubMed
For
Is RSD caused by psychological issues? enter the search term
Reflex Sympathetic Dystrophy/*psychology
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nerve blocks/RSD try the search term
"Nerve Block"[MeSH] AND "Complex Regional Pain Syndromes"[MeSH] and the partially overlapping
"Nerve Block"[MeSH] AND "Complex Regional Pain Syndromes"[MeSH]
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ketamine/ RSD enter the search term
Complex Regional Pain Syndromes AND ketamine