Legal Question in Family Law in Nevada

No responsible attorney would say that any one specific fact is "the" deciding factor, but certainly each parent's mental and physical health is on the list -- and there is a list of factors a judge is required to consider in making a custody decision. For a link to that statute, plus a lot of other resources (explanations, flowcharts, some videos, links to the controlling cases, etc., see https://www.willicklawgroup.com/child-custody-and-visitation/.