Short answer: no. Long answer: yes. Welcome to the complex world of gene-environment interactions.
Concussions are not safe by any means; they might put you at risk for memory problems or an earlier onset of dementia. The good news is that if your genes are healthy, a concussion probably won’t spontaneously give you schizophrenia. The bad news is some people have hidden risk factors for the disease that can come out if conditions are right.
Schizophrenia and autism are both spectrum disorders. Autism can range from the mild awkwardness of Asperger’s (think Sheldon Cooper) to an inability to speak. Like autism, schizophrenia is a little different for everyone. Some may have negative symptoms like low IQ, memory loss, or lack of emotion. Others have more positive symptoms like hallucinations or delusions.
Where do these differences come from? Schizophrenia is not a simple disease like diabetes or cystic fibrosis, where one gene is defective. It seems like schizophrenia comes from a combination of many different gene mutations. Obviously, having more mutations is worse, but some mutations are worse than others. One schizophrenic patient might have a half-dozen small mutations adding up, while another patient has one or two extremely destructive mutations. So the different combinations of risk factors explains some of the differences in severity as well as symptoms.
Stay with me while I throw one more thing into the mix: life experiences. Remember Walter White’s “fugue state”? He woke up with no memory of why he was standing naked in the produce aisle. Supposedly, the stress of having terminal cancer, a disabled son, and a newborn daughter (not to mention a drug empire) was enough to drive him temporarily insane. Walt was faking of course, but trauma can have real lasting effects on a person’s mental health.
Imagine a freshman on the football field. He has two mutations affecting his neurons. Maybe a protein is slightly out of shape, or he’s overproducing some neurotransmitter. But it’s nothing his brain can’t handle. Then along comes a fifth-year senior with a full beard, and he’s on the ground tasting the color purple. That hit was enough to push him over the threshold into full-blown schizophrenia. Like many others, he starts developing symptoms at around age 20, with his high school concussion long forgotten.
Denmark to the rescue! Using their obsessive record keeping, a study in 2014 had access to 100,000 participants with head trauma. That huge sample size makes the study very reliable. The study found that head trauma increased the risk of schizophrenia by 65%. Other studies (here and here) have shown that a family history of schizophrenia increases the risk even more.
Trauma, whether psychological or physical, has frightening power to reveal and magnify hidden disorders. At this point in modern medicine, there’s still no way of knowing for sure who is at risk. For now, please wear a helmet.
