Nature Mental Health, Published online: 05 May 2026; doi:10.1038/s44220-026-00622-8
Difficulty updating one’s beliefs to reflect changing circumstances — ‘belief stickiness’ — might underpin some forms of inflexibility. We found that increasing serotonin decreased belief stickiness and that obsessions were associated with increased belief stickiness. These findings uncover a new role for serotonin and could have implications for the treatment of obsessions.