 Since the humoral theories of earlier eras, mood disorders have been strongly associated with bodily  states.[8]  Chief among the several hypotheses about depression challenged by philosophers are appeals to hormonal changes and biology (particularly as they would explain depression’s persistent gender link), and accounts derived from evolutionary psychology (Varga 2012, 2016; Bluhm 2011). Related work also emphasizes that explanations of depression must appeal to broader societal structures, rather than individual vulnerabilities (Bluhm 2011; Bluhm, Jacobson, &amp; Maibom 2012)). The uncertain line between disorders of mood and normal states of distress was discussed earlier  (§4.2).  It has prompted contrasting hypotheses about “true” depression, as we saw, including inferences to brain dysfunction (Horwitz &amp; Wakefield 2007), and criteria that appeal to a disabling degree of suffering (Bolton 2013).