" It goes without saying that all mental illnesses are neurologically instantiated, but this says nothing about their causation. If it is true, for instance, that depression is constituted by low serotonin levels, what still needs to be explained is why particular individuals have low levels of serotonin. This requires a social and political explanation; and the task of repoliticizing mental illness is an urgent one if the left wants to challenge capitalist realism. "

― Mark Fisher , Capitalist Realism: Is There No Alternative?