However, the concentration trend of serum FGF-2 levels was completely different between groups (effect sizes = −2.118, p = 0.034); while MDD patients showed a distinct decline after treatment (d = 18.36 ± 94.06, p = 0.016), BPD patients maintained an insignificant change (d = −4.74 ± 92.58, p = 0.270) compared to the baseline level. Here, FGF2 is linked to major depressive disorder.