Sylvia Nasar said this quote

...his condition in Roanoke is a strong testament that lassitude, indifference and the peculiarities of his thought were primarily the consequences of his illness and not of the early attempts to treat it. The popular view that anti-psychotics were chemical straight jackets that suppressed clear thinking and voluntary activity seems not to be borne out in Nash's case.If anything, the only periods when he was relatively free of hallucinations, delusions and the erosion of will were the periods following either insulin treatment or the use of anti psychotics. In other words, rather than reducing Nash to a zombie, medication seemed to reduce zombie like behavior.

~ Sylvia Nasar

Store speculates:Some creative people… of predominantly schizoid or depressive temperaments... use their creative capacities in a defensive way. If creative work protects a man from mental illness, it is a small wonder that he pursues it with avidity. The schizoid state... Is characterized by a sense of meaninglessness and futility. For most people, interaction with others provides most of what they require to find meaning and significance in life. For the schizoid person, however, this is not the case. Creative activity is a particularly apt way to express himself... The activity is solitary... [but] the ability to create and the productions which result from such ability are generally regarded as possessing value by our society.

~ Sylvia Nasar