Susan Pinker on how a concussion was both a personal struggle for her and a catalyst to study a phenomenon still only partly understood

See the column on the Wall Street Journal site

Eighteen months ago, a pickup truck hit me while I was walking on the sidewalk. The last thing I remember from that sunny Tuesday morning was reaching for my car keys. Then the lights went out.

I regained consciousness while being slid out of the scanner in the trauma unit. I had two fractures, two torn tendons, some wicked road rash and a concussion. The accident shook up my relationships, my memory and my personal drive. Still, everyone told me I was lucky to be alive, and I agree. Life has never seemed as tenuous—or as precious.

Not everyone with a mild brain injury is as lucky. A 20-year study published in February in the Canadian Medical Association Journal shows that people who have had a mild concussion are twice as likely to commit suicide as military personnel and more than three times as likely as members of the general population. Most of us agree with the bromide that time heals all wounds, but this study showed the opposite: After the concussion the risk of suicide rose steadily over time.

Led by Donald Redelmeier, a professor of medicine at the University of Toronto, the study included 235,110 healthy people who had seen a doctor after their accident. Most of the patients had no prior psychiatric diagnosis, hospital admission or suicide attempt.

“In the aftermath of a crash there is tremendous agony. But the broken ribs and leg will heal,” Dr. Redelmeier told me. “I’m not as sanguine about a concussion. Even when the CT scan doesn’t show major trauma, a minor injury can damage thousands and thousands of neurons. There are all sorts of problems that can last a long time, and we don’t know how to treat them.”

That clinical gap was clear. As I was leaving the emergency room, a staffer handed me a tip sheet written for teenage hockey players. (I live in Canada, after all.) There was no information for adults, nor anything on women and girls—who are known to be at greater risk of long-term problems after a concussion. When I asked the surgeon about cognitive symptoms during a follow-up visit, he exclaimed, “One concussion! The risk comes with more than one knock.” He added, “You’ll be fine.”

But I was far from fine. I spent mornings doing media interviews by phone about my new book, trying to sound upbeat. I spent afternoons sleeping, sobbing or staring at the clock, willing the time to pass so I could take another dose of oxycodone.

Meanwhile, well-meaning friends and colleagues were suggesting that the accident was some sort of warning. “This is God’s way of telling you to slow down,” said one. “Were you texting? Wearing headphones?” asked another. The refrain was that I should be thankful I’d dodged a karmic bullet and just get on with things.

But life was very different. A year after the accident I invited a friend to a concert—then blithely went on my own, forgetting all about her. I napped like a toddler and, because of fatigue and shoulder pain, couldn’t work a full day. I was never suicidal, thank goodness. But I was racked by an unanswered question: Why did this happen?

That lack of closure leads to one of the most astounding of Dr. Redelmeier’s findings. Compared to weekday accidents, weekend concussions magnify one’s suicide risk. One explanation could be psychological, he said. “If you get hurt at work, you can blame the circumstances. But if you get hurt horseback riding, that might affect how much support and sympathy you get, whether there’s companionship in fighting the good fight, or whether people feel you’re the architect of your own misfortune.”

Understanding why something happened is as important to brain health as a cast is to bone strength, it seems. It turns out that I am lucky, after all. I may never know why the driver didn’t see me. But I do know one thing: I was working that day, and it was a Tuesday.