How Much Does Social Isolation Slow Down Recovery from Brain Injury? PTSD?

I had a thought (I know, so odd): how much does social isolation, systemic inaccessibility, and opprobrium from family, friends, lawyers, health care professionals, etc. slow down recovery from brain injury and/or PTSD? We’ve read of studies* showing positive effects on the heart of socially cohesive neighbourhoods, lifelong negative effects on children of lack of…