My psych professor would agree with you (and it's part of the reason I'm convinced I need to move to my own place). We recently read a psychiatrist's suggestions for better design of mental hospitals in which he noted that mental patients who have their own private rooms have a greater sense of security because they've got somewhere safe to go back to when they're overwhelmed. That way they don't withdraw internally, and feel more in control of their own socialization.

I might actually seek more human contact if I were not forced by necessity to live with strangers and people who turned out to be jerks, so I'm totally in agreement with your theory.