Deviant peer affiliations and depression: confounding or causation?

Data gathered from 2 longitudinal studies (the Christchurch Health and Development study of a birth cohort of 1,265 New Zealand participants studied to 21 years and the Quebec Study of 240 Canadian participants studied to 13 years) was used to examine the linkages between deviant peer affiliations and depression in adolescence. Both studies produced similar conclusions: a) increasing peer affiliations were associated with significant (p < .0001) increases in depressive symptoms; b) the associations between peer affiliations and depression could not be fully explained by confounding factors; and c) peer affiliations and depressive symptoms were linked by a causal chain process in which deviant peer affiliations led to increased externalizing behaviors with the negative consequences of these behaviors leading to depression.