Elevated C-reactive protein is associated with suicide attempts in youth with bipolar disorder

C-reactive protein (CRP) has been studied in relation to bipolar disorder (BD) and suicidality independently. Although suicide risk is elevated in youth with BD, little is known about the association of CRP with suicidality in this population.

211 youth participated, including 23 BD with lifetime suicide attempts (BD_SA), 45 BD with lifetime non-suicidal self-injury (NSSI; BD_NSSI), 39 BD without lifetime suicide attempt or NSSI (BD_No-SA/NSSI), and 104 healthy controls (HC). Suicide attempts and NSSI were assessed systematically. Fasting blood samples yielded CRP levels. Primary analyses controlled for age, sex, and body mass index percentile.

CRP levels differed across groups (F_3,204 = 3.40, p = 0.02, η_p² = 0.05). In post hoc analyses, CRP levels were significantly higher among BD_SA (3.44 ± 6.42 mg/L) vs HC (0.81 ± 0.90 mg/L; p < 0.01) and BD_No-SA/NSSI (1.42 ± 3.31 mg/L; p = 0.01) groups; however, no difference was seen with the BD_NSSI group (1.83 ± 2.22 mg/L; p = 0.12). Between-group differences in CRP levels persisted in independent sensitivity analyses controlling for current mood symptoms, lifetime mania score, lifetime smoking, and medications, but not with lifetime depression score.

Suicide attempts among youth with BD are associated with elevated CRP. Given accessibility of CRP testing, the present findings have potential clinical implications. Larger, longitudinal studies with repeated measures are needed to examine time-varying associations between CRP and suicide risk among youth with BD.