Children who are abused and neglected are more likely to experience chronic inflammation and depression as adults, according to this piece from Science Daily.
Andrea Danese of King's College London carried out the study of 1,000 New Zealanders born in 1972 or 1973. She evaluated them every three years until they were 32. According to the article,
Individuals with current depression and a history of childhood maltreatment were more likely to have a high level of inflammation at age 32, as measured by the presence of the chemical high-sensitivity C-reactive protein in the blood. Those with depression but no history of childhood maltreatment did not have this increased risk.
I think that this inflammation is related to a weak oxytocin response. Oxytocin is the anti-cortisol, soothing inflammation and promoting healing. Our brains develop the oxytocin response after we're born, in response to the care and soothing we get from our primary caregiver, most often our mothers. If our mothers don't provide that care, we never learn to let go with this calming, healing neurochemical/hormone.
This study shows another way that love and connection with others are tied to physical health.
See also, Neglect as Damaging as Abuse for Kids.