AbstractBackgroundMood swings have been observed in patients with intracranial aneurysm (IA), but it is still unknown whether mood swings can affect IA.AimTo explore the causal association between mood swings or experiencing mood swings and IA through a two‐sample Mendelian randomization (MR) study.MethodsSummary‐level statistics of mood swings, experiencing mood swings, IA, aneurysm‐associated subarachnoid hemorrhage (aSAH), and non‐ruptured IA (uIA) were collected from the genome‐wide association study. Two‐sample MR and various sensitivity analyses were employed to explore the causal association between mood swings or experiencing mood swings and IA, or aSAH, or uIA. The inverse‐variance weighted method was used as the primary method.ResultsGenetically determined mood swings (odds ratio [OR] = 5.23, 95% confidence interval (95%CI): 1.65–16.64, p = .005) and experiencing mood swings (OR = 2.50, 95%CI: 1.37–4.57, p = .003) were causally associated with an increased risk of IA. Mood swings (OR = 5.67, 95%CI: 1.40–23.04, p = .015) and experiencing mood swings were causally associated with the risk of aSAH (OR = 2.91, 95%CI: 1.47–5.75, p = .002). Neither mood swings (OR = 1.95, 95%CI: .31–12.29, p = .478) nor experiencing mood swings (OR = 1.20, 95%CI: .48–3.03, p = .693) were associated with uIA.ConclusionsMood swings and experiencing mood swings increased the risk of IA and aSAH incidence. These results suggest that alleviating mood swings may reduce IA rupture incidence and aSAH incidence.