Can things have multi-factor causes? It seems plausible that high environmental lead levels contribute (with at least a small effect size) to violence and crim

Can things have multi-factor causes? It seems plausible that high environmental lead levels contribute (with at least a small effect size) to violence and crime. If a lead-free environment is already violent and insecure, would you expect adding environmental lead to make it less violent, more violent, or the same?