Current state and future directions of biomarkers for bipolar disorder: A systematic review of studies from 2013 to 2025 Publication date: October–December 2025 Source: The European Journal of Psychiatry, Volume 39, Issue 4 Author(s): Guocan Ma, Fengyi Hao, Soon-Kiat Chiang, Dewen Zhou, Roger C. Ho, Roger S. McIntyre