Risk of depression influenced by quality of relationships, research says - full text

"The mantra that quality is more important than quantity is true when considering how social relationships influence depression, say U-M researchers in a new study.
"After analyzing data from nearly 5,000 American adults, the researchers found that the quality of a person's relationships with a spouse, family and friends predicted the likelihood of major depression disorder in the future, regardless of how frequently their social interactions took place...."

http://medicalxpress.com/news/2013-04-depression-quality-relationships.html

Full text:

Social Relationships and Depression: Ten-Year Follow-Up from a Nationally Representative Study

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0062396