History of Concussion and Risk of Severe Maternal Mental Illness: A Population-Based Cohort Study

Objective: To evaluate the relationship between a predelivery history of concussion and risk of severe maternal mental illness.

Methods: We conducted a population based cohort study of birthing people with a singleton livebirth accrued between 2007 and 2017 with follow-up to 2021 in Ontario, Canada. The primary outcome was severe maternal mental illness, defined as a psychiatric emergency department visit, psychiatric hospital admission, or self-harm or suicide in the 14 years after delivery. Cox proportional hazards regression generated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) comparing those with a history of a health care encounter for concussion between database inception and the index delivery date to those without a recorded health care encounter for concussion, adjusted for maternal age, parity, neighborhood income quintile, rural residence, immigration status, chronic conditions, history of interpersonal violence, and history of mental illness. Results were also stratified by history of mental illness.

Results: There were n = 18,064 birthing people with a history of concussion and n = 736,689 without a history of concussion. Those with a history of concussion had an increased risk of severe maternal mental illness compared to those without this history (14.7 vs 7.9 per 1,000 person-years; aHR 1.25, 95% CI, 1.20-1.31). After stratification by predelivery history of mental illness, the association was strongest in individuals with no mental illness history (aHR 1.33, 95% CI, 1.23-1.44).

Conclusion: These findings indicate the need for early identification and screening of birthing people with a history of concussion, as well as ongoing long-term supports using trauma informed approaches to prevent adverse psychiatric outcomes.