Concussion multiplies the long-term risk of suicide in adults, especially if it happens on the weekend, according to research published in the CMAJ.

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Concussion symptoms abate quickly, but the long-term effects can be severe.

Suicide is the 10th most common cause of death in the US, with 41,149 cases in 2011, or 13 per 100,000 people, according to the Centers for Disease Control and Prevention (CDC). It is normally associated with a psychiatric illness, such as depression or substance abuse.

Concussion is the number one brain injury in adults, affecting around 4 million Americans each year. It is defined as "a transient disturbance of mental function caused by acute trauma."

Symptoms are usually resolved quickly, so that physicians may underestimate the dangers of concussion and its long-term effect.

Concussion has been associated with depression, and previous studies have established a link between concussion and suicide among military veterans. The researchers point out that military personnel are not the only group affected.

Researchers from the University of Toronto, the Institute for Clinical Evaluative Sciences (ICES) and Sunnybrook Research Institute, all of Toronto, in Canada, and the Canadian Armed Forces collaborated to find out more about a potential link.

They accessed records from the health insurance database for 235,110 patients who had a concussion over a 20-year period. The patients were aged 41 years on average, evenly split between genders, and most lived in cities. The majority had no suicide attempt, hospitalization or past psychiatric disorder.

Comparison of weekend and weekday concussion

The team compared weekend and weekday concussions to distinguish between recreational and occupational injuries. They speculated that this could affect the severity and mechanism of injury. Recreational injuries are more common on weekends, and occupational injuries tend to happen on weekdays.

The distinction could be significant in terms of repeat concussions, the likelihood of using protective gear, the tendency to seek and adhere to medical attention, the availability of medical care and other factors.

In the 9.3 years following the concussion, 667 suicides occurred.

Weekday concussion incidents were associated with 519 suicides, or 29 per 100,000 people. This was triple the rate for the general population of Canada, and higher than that for military personnel. There were 148 suicides among weekend concussion patients. At 39 per 100,000, this was four times the population norm.

Concussion has been shown to increase the chance of depression. In this study, the long-term risk of suicide persisted among those who had no psychiatric risk factors. Compared with patients who experienced an ankle sprain, people with concussion had a far greater risk of suicide.

On average, the length of time from concussion to suicide was 5.7 years, and the average age at death was 44 years. Additional concussions appear to increase the risk of suicide further.

Most patients had visited their family physician in the month prior to the suicide; most of the suicides resulted from a drug overdose.

The authors hope the study will raise awareness of the risks of concussion for patients and clinicians.

Dr. Donald Redelmeier, senior core scientist at ICES and a physician at Sunnybrook, says:

"Greater attention to the long-term implications of a concussion might save lives because deaths from suicide can be prevented."

Medical News Today recently published an article advising rest after concussion to prevent progressive damage.