Most social scientists have tended to assume that poverty predisposes
to mental disorder, on the grounds that numerous studies have shown statistical
associations between the two.1,2 However,
as Costello et al3 point out in this issue
of THE JOURNAL, causal inference is problematic in the absence of experimental
evidence because of the crucial need to differentiate between social selection
and social causation.4,5 In other
words, does the statistical association reflect the tendency for individuals
with mental disorder to drift into or remain in poverty, or does the experience
of poverty itself predispose to mental disorder?