1. A large, retrospective population-based cohort study of over 150, 000 participants found an association between concussion and risk of future mental health issues in children aged 5-18 with no previous history of psychiatric diagnoses.

2. Increased risk of mental health issues, self-harm and psychiatric hospitalization was found in children who had suffered a concussion compared to those who had suffered an orthopedic injury.

Evidence Rating Level: 2 (Good)

Study Rundown: Minor traumatic brain injuries, otherwise known as concussions, are extremely common and frequently underrecognized. Concussions account for a significant proportion of healthcare visits, particularly amongst children. Despite their commonness, little is known about the long-term impact of concussions. Previous studies have postulated that various psychiatric, behavioral and emotional symptoms may be problematic in the weeks and even months following a concussion, although much of this work has been of poor quality and it is difficult to derive clinically meaningful data. The present retrospective, population-based cohort study sought to describe the relationship between concussion and mental health risks in children and adolescents over a 10 year period. A total of 152,321 eligible patients were found to have had a concussion during the study period and matched with 296,482 control subjects who had orthopedic injuries. A significant association was found between the concussion group and risk of mental health problems. Specifically, children who had had a concussion were more likely to have anxiety, neurotic disorders, adjustment reactions, mood and behavioral disorders compared to the control group. A significant association between concussion and risk of self-harm was also identified, as was the association between concussion and psychiatric hospitalization. Risk of dying by suicide was not statistically significantly different between groups. This population-based retrospective cohort study identified a strong link between concussion history and risk of subsequent mental health concerns amongst children aged 5-18 in Ontario. This information is crucial in alerting families, childcare providers and physicians as to the importance of identifying concussions, managing them appropriately and watching for complications. Clinically useful future research should seek to characterize the timeline over which mental health concerns may develop, and develop interventions to reduce this risk. This study is strengthened by the large sample size and longitudinal follow up time. However, the nature of the study design renders it susceptible to misclassification bias as well as confounding variables.

Click here to read this study in JAMA Network Open

Click to read an accompanying editorial in JAMA Network Open

Relevant reading: Mental health after paediatric concusssion: a systematic review and meta-analysis

In-depth [retrospective cohort study]: Data from several databases under the the Institute for Clinical Evaluative Sciences (IC/ES) umbrella were linked. Patient data were derived from children and youth who visited the Emergency Department (ED) following a concussion in Ontario, Canada between April 1, 2010 to May 31, 2020. These cases were matched on a 1:2 basis to children in the ED who had suffered an orthopedic injury, but no concussion. Matching was done on the basis of age and sex. Participants were excluded if they were known to have experienced a concussion within 5 years of the index event, or a mental health issue either before, or at the time of their hospital visit. Exposure status and eligibility were determined using International Code for Disease classification coding. The primary outcome of a mental health issue encompassed the following conditions: anxiety, neurotic disorders, adjustment reaction, behavioral disorders, eating disorders, mood disorders, schizophrenia, substance use disorders, suicidal ideation and developmental concerns. The rate of mental health problems per 100,000 person-years in the experimental group was 11,141 (95% confidence interval [CI], 11,048-11,236) compared with 7960 (7905-8015) in the control group. The adjusted hazard ratio between groups was 1.39 (1.37-1.40). The rate of self-harm in the concussion group was 475/100,000 person years (459-492) and 327/100,000 person-years (317-327) in the control group. The adjusted hazard ratio for self-harm was 1.49 (1.42-1.56).  Finally, the rate of psychiatric hospitalization in children who had a concussion was 623/100,000 person-years (604-643) and 434/100,000 person-years (442-446) in those who had not. The adjusted hazard ratio for psychiatric hospitalization was 1.47 (1.41-1.53). These associations were robust to sensitivity analysis which introduced the possibility of future concussions during the follow up period. The adjusted hazard ratios and corresponding 95% confidence intervals were as follows: 1.34 (1.33-1.36) for mental illness, 1.42 (1.36-1.48) for psychiatric hospitalization and 1.44 (1.38-1.52) for self-harm. The risk of dying by sucide was not significantly different between the concussion and orthopedic injury groups (adjusted hazard ratio 1.54, 95% CI 0.90-2.62).

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