Is the incidence of depressive disorders increased following cerebral concussion?
EVIDENCE-BASED ANSWER
Yes, in some populations. Youth and adolescents with self-reported history of concussion had increased risk of depressive disorders (strength of recommendation [SOR]: B, based on a prospective cohort study and a retrospective cohort study). Evidence was inconsistent for college athletes. Athletes with ≥ 3 concussions exhibited more depressive disorders, but no association was observed for those with 1 or 2 concussions compared to nonconcussion injuries (SOR: B, based on a cross-sectional study, a small prospective cohort study, and a case-control study).
In semiprofessional and professional athletes, evidence was variable and may be sport related. Retired rugby players with a history of concussion showed no increase in depression compared to controls with no concussion history (SOR: B, based on a case-control study). Retired football players with previous concussions displayed increased incidence of depression, especially after ≥ 3 concussions (SOR: B, based on a prospective cohort study and a small case-control study).
There is a significant risk of bias in these studies because of their reliance on self-reported concussions, differing definitions of depression, and possible unmeasured confounders in the study designs, making a causative relationship between concussion and depression unclear.
While both groups showed a significant increase from baseline CES-D scores, there were no significant differences in depressive symptoms between concussed (mean CES-D score ± standard deviation [SD]: baseline, 6.7 ± 3.9; 1 week, 11 ± 5.3; 1 month, 8.3 ± 5; 3 months, 6.4 ± 5.4) and injured but nonconcussed participants (mean CES-D score ± SD: baseline, 5.7 ± 2.8; 1 week, 9.1 ± 4; 1 month, 8.9 ± 4.6; 3 months, 6.9 ± 2.8) at any of the postinjury time points.
Findings among semipro and pro athletes appear to vary by sport
A 2016 prospective cohort study assessed the impact of concussive events on incidence of depression in active semiprofessional and professional football players who had previously sustained ≥ 1 concussions.6 Participants (N = 27) answered an anonymous online survey that included the revised version of the CES-D (CESD-R) to determine level of depression (a score of ≥ 16 defined clinical depression). Players with a CESD-R score ≥ 16 (N = 16) sustained a significantly greater average number of concussions compared to those who scored < 16 (N = 11; 3.8 vs. 1.6, P = .0004). Players who sustained ≥ 3 concussions scored significantly higher on the CESD-R than players with ≤ 2 concussions (average score, 24 vs 15.6; P = .03).
A 2017 case-control study examined the long-term health outcomes of retired Scottish male rugby players (N = 52; mean age, 54 years) with a history of mild concussion compared to males of similar age with no previous history of concussion (N = 29; mean age, 55).7 The Hospital Anxiety and Depression Scale (HADS) was used to assess depression on a 21-point scale (normal = 0-7; borderline, 8-10; abnormal, 11-21). There was no significant difference observed in mean HADS scores between the rugby players and controls, respectively (2.8 ± 2.1 vs 2.6 ± 2 .8; P = .941).
A 2013 case-control study of 30 retired NFL players with 29 controls matched for age, estimated IQ, and education examined the relationship between a remote history of concussion and current symptoms of depression.8 Concussion history was self-reported by the retired players. Controls with a history of concussion were excluded from the study. The Beck Depression Inventory-II (BDI-II) was used to measure depression symptoms, with a score of 1 to 9 designating minimal depression and ≥ 10 mild-to-moderate depression. Retired players scored significantly higher on the BDI-II compared to the controls (8.8 vs 2.8; P = .001).
Editor’s takeaway
Concussions include cognitive compromise. An astute clinician’s concern for depression as a sequela makes sense. This evidence contributes to that conjecture. However, the authors of this Clinical Inquiry correctly outline the limitations, inconsistencies, and biases of the evidence. The exact relationship—degree and context—between concussion and depression remains vague.
