11. He was described as having a difficult personality by his contemporaries
One of the arguments put forth to support the theory that Isaac Newton suffered from what is now known as bipolar disorder is the difficult nature of his personality. Newton’s contemporaries, both friend and foe, described him in less than flattering terms when discussing his social skills. “The most fearful, cautious, and suspicious temper, than I ever knew,” wrote William Whiston, who served as Newton’s deputy in 1701, when Newton held the Lucasian Mathematics chair at Trinity College. Whiston also performed the majority of the duties associated with the position, which Newton turned into a sinecure, not tutoring students or concentrating on the performance of the students in the department. His personality wouldn’t allow him to teach.
When Newton attained his status as a Master of Arts and Major Fellow at Trinity College he began receiving a small stipend from the college, and continued to receive annual support from his mother, which he used beginning in early 1668 to refurbish his rooms. After the college itself took care of the heavy construction Newton had the interior redone to his taste, and went on a spending spree, purchasing carpets, leather chairs, ten additional chairs, several tables and desks, chests, a sofa, glasses, table linens, and a new bed. The spending on his refurbished home has been described by those supporting the theory of bipolar disorder as being symptomatic of a manic phase.