Researchers have long studied the link between creativity and mental illness, and the lines between the two are often blurred. Research suggests that creative people often share more personality traits with the mentally ill than “normal” people in less creative pursuits. One study compared patients with bipolar disorder with a group of healthy people. It was found that graduate students in creative disciplines shared more personality traits with the bipolar patients than with their healthy but less creative peers.

Strong CM, Nowakowska C, Santosa CM, Wang PW, Kraemer HC, Ketter TA.
Temperament-creativity relationships in mood disorder patients, healthy controls and highly creative individuals. Journal of affective Disorders, 2007;100(1-3):41-8.

OBJECTIVE: To investigate temperament-creativity relationships in euthymic bipolar (BP) and unipolar major depressive (MDD) patients, creative discipline controls (CC), and healthy controls (HC).

METHODS: 49 BP, 25 MDD, 32 CC, and 47 HC (all euthymic) completed three self-report temperament/personality measures: the Revised NEO Personality Inventory (NEO-PI-R), the Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A), and the Temperament and Character Inventory (TCI); and four creativity measures yielding six parameters: the Barron-Welsh Art Scale (BWAS-Total, BWAS-Like, and BWAS-Dislike), the Adjective Check List Creative Personality Scale (ACL-CPS), and the Torrance Tests of Creative Thinking–Figural (TTCT-F) and Verbal (TTCT-V) versions. Factor analysis was used to consolidate the 16 subscales from the three temperament/personality measures, and the resulting factors were assessed in relationship to the creativity parameters.
RESULTS: Five personality/temperament factors emerged. Two of these factors had prominent relationships with creativity measures. A Neuroticism/Cyclothymia/Dysthymia Factor, comprised mostly of NEO-PI-R-Neuroticism and TEMPS-A-Cyclothymia and TEMPS-A-Dysthymia, was related to BWAS-Total scores (r=0.36, p<0.0001) and BWAS-Dislike subscale scores (r=0.39, p<0.0001). An Openness Factor, comprised mostly of NEO-PI-R-Openness, was related to BWAS-Like subscale scores (r=0.28, p=0.0006), and to ACL-CPS scores (r=0.46, p<0.0001). No significant relationship was found between temperament/personality and TTCT-F and TTCT-V scores.
CONCLUSIONS: Neuroticism/Cyclothymia/Dysthymia and Openness appear to have differential relationships with creativity. The former could provide affective (Neuroticism, i.e. access to negative affect, and Cyclothymia, i.e. changeability of affect) and the latter cognitive (flexibility) advantages to enhance creativity. Further studies are indicated to clarify mechanisms of creativity and its relationships to affective processes and bipolar disorders.