Drift hypothesis, concerning the relationship between mental illness and social class, is the argument that illness causes one to have a downward shift in social class.[1] The circumstances of one's social class do not cause the onset of a mental disorder, but rather, an individual's deteriorating mental health occurs first, resulting in low social class attainment.[2] The drift hypothesis is the opposing theory of the social causation thesis, which says being in a lower social class is a contributor to the development of a mental illness.