As Sidis entered early adulthood, he was working toward careers in mathematics and law when he also began to embrace (at various points) a number of ideologies and outlooks on life including pacifism, socialism, atheism, and libertarianism (via Swarthmore). Criminally punished for his participation in socialist events, he spent several months in his psychiatrist father’s sanitarium to avoid jail time. After this, he became increasingly reclusive, writing for publications under different pseudonyms as the public largely forgot him (via History Of Yesterday). Before and during his seclusion he wrote many books on the topics of his expertise, political opinions, and interests, such as public transportation. 

Toward the end of his life, Sidis largely made a living as an office clerk while living alone in a small apartment (via All That’s Interesting). In 1937, The New Yorker located Sidis and published an exceptionally unflattering piece on his then-current living conditions. In later years he would seek restitution in court over the blatant invasion of his privacy but his case was dismissed in 1944. That same year Sidis, who at least in his time was considered the smartest man in the world, died of a brain hemorrhage at the age of only 46.