Researchers have found that suffering even a minor concussion can lead to loss of sense of smell. 

It's long been known that people who suffer a major concussion can lose their sense of smell temporarily and also develop effective problems, such as anxiety and depression. Now, as part of the latest study, scientists have found that's true even for people who get a minor concussion. In a study published in Brain Injury, a team of researchers compared 20 hospital patients who had mild concussions to 22 who'd broken limbs but had no concussion. 

Within 24 hours of their accident, just over half of those with mild concussions had a reduced sense of smell, versus only 5 per of the patients with broken bones. A year later, although their sense of smell was back to normal, the first group of patients had significantly more anxiety than the control group. 

"A lot of people will suffer a mild concussion at some point in their life, so realizing they have trouble smelling is the first step to telling their doctor about it. It's important that patients report any loss of smell because it's not something their general practitioner or emergency-room physician normally asks about," said lead author Fanny Lecuyer Giguere. 

According to the researchers, identifying the problem is a short step to getting personalized treatment, with closer follow-up to see if the loss of smell and anxiety persist, indicating the severity of the injury. 

Physicians should also educate their patients so that they check whether symptoms crop up in the weeks following their accident. 

To test their capacity to identify smells, researchers visited hospital patients in the alpine ski resort of Visp, Switzerland between December 2016 and February 2017. Almost all those with mild concussions had had a skiing accident. 

They were all seen within the first 24 hours following their accident, as were those with fractures but no concussion. With scented "Sniffin' Sticks' (felt-tip pens) to smell, they were asked to identify synthetic odours of roses, garlic, cloves and solvent, and more. 

A year later, the patients were sent a follow-up questionnaire and a set of scratch-and-sniff booklets. By comparing the two groups of patients' results in the day following their injury and 12 months later, the researchers were able to determine that most who'd lost their sense of smell gained it back within six months of their accident. 

What did not significantly diminish, however, were their symptoms of anxiety: thoughts that made them worry, difficulties to relax, and sudden feelings of panic. About 65 per cent of the concussed patients reported such symptoms.