This study examined the use of dynamic amplitude low-frequency fluctuations (dALFF) to differentiate bipolar disorder (BD) and major depressive disorder (MDD) at an early stage, with a focus on sex-specific brain activity. The study included 35 patients with BD who converted from MDD, 99 MDD patients, and 130 healthy controls (HCs). Key findings showed distinct dALFF patterns in the frontal and occipital gyrus regions, with patients with MDD exhibiting higher values in certain brain areas compared to BD patients and HCs. Sex differences were also observed, with males showing higher dALFF in the left middle occipital gyrus and medial superior frontal gyrus, while female patients with BD had higher dALFF than their male counterparts.

The study revealed a significant interaction between sex and diagnosis in the right precentral gyrus, where male MDD patients had higher dALFF than male patients with BD, while female BD patients had greater dALFF than male patients with BD. These results suggest that sex-specific neurobiological mechanisms may play a role in distinguishing BD and MDD early on. Additionally, the study highlighted the link between cognitive function and dALFF values in patients with MDD, where executive function was positively correlated with dALFF in specific brain regions. The findings emphasize the importance of considering both sex and brain activity in the early diagnosis of BD and MDD.

Reference: Liu W, Jiang X, Xin Y, et al. Sex effects on differentiating patients with major depressive disorder from bipolar disorder in depressive state: A fMRI study with follow-up. J Affect Disord. 2023 Nov 1;340:396-404. doi: 10.1016/j.jad.2023.08.041. Epub 2023 Aug 11. PMID: 37572701.