There is an often-cited quote by Virginia Satir, saying
“We need 4 hugs a day for survival.
We need 8 hugs a day for maintenance.
We need 12 hugs a day for growth.”
Traina, C. (2005). Touch on Trial: Power and the Right to Physical Affection. Journal of the Society of Christian Ethics states the following (emphasis mine):
This essay's thesis is simple and seemingly quixotic: Affectionate, firm, apprpriate touch is a human need and a moral right. Infants and children require attentive, affetctionate, intimate touch from adults in order to thrive.
Floyd, K. (2015). Affection Exchange Theory. In The International Encyclopedia of Interpersonal Communication (eds C.R. Berger, M.E. Roloff, S.R. Wilson, J.P. Dillard, J. Caughlin and D. Solomon). states (emphasis mine):
Affectionate communication is fundamental to the human relational experience. Across cultures, the expression of affection contributes to the formation, maintenance, and satisfaction level of close personal relationships. Floyd's affection exchange theory (AET) proposes that affectionate communication evolved among humans due to its contributions to the important goals of survival and procreation. This article introduces and evaluates AET, and details empirical work identifying the benefits of affectionate behavior for relationships and individual physical and mental health.
This suggests that physical intimacy is a necessity for survival. However, I was unable to find any studies that showed that there were clear, observable and repeatable adverse effects on human adults from a lack of physical affection. Are there any studies on that matter?