How do childhood relationships and experiences affect the likelihood of being depressed in adult life?
There's some very interesting data here. In the Freudian days, depression was all about early childhood, and then I think we lost sight of that with the spectacular introduction of medication. But now we're coming around to seeing the importance of the gene/environment interaction.
There are some data that show that children who have been abused or who have had very difficult relationships at home are more vulnerable to depression, particularly if they carry the genetic vulnerability.
This is what makes psychotherapy very important, because you can't intervene in genes but you can help the person cope with their environment.