Friendships and adaptation in the life course.

To consider friendships and their significance through the life course requires, first, differentiation of deep structure (i.e., reciprocity) from surface structure (i.e., the social exchange) and, second, assessment within a multifaceted framework that simultaneously emphasizes having friends, the identity of one's friends, and relationship quality. Having friends is correlated with a sense of well being across the life span, but developmental outcome also depends on the identity of one's friends as well as the quality of one's relationships with them. Greater attention needs to be given to the manner in which friendships differ from one another, continuities and changes across major developmental transitions, and differentiation of developmental pathways through which friendship experience contributes to individual outcome.