More than 2 million people worldwide have MS, a disease that often compromises the ability to walk and move. It is known that depression is a risk factor for multiple sclerosis and that depression is more common in people with multiple sclerosis, but so far it has not been clear whether mental illness can also be linked to the rate of progression of multiple sclerosis.
In this study, the researchers compared the course of the disease in nearly 1,800 MS patients who were depressed with about 7,900 MS patients who were not depressed for up to 13 years. They found that patients with depressed MS had a risk of nearly 90 percent more reaching a state where they needed a cane to walk 100 meters than those who were not depressed. This was also the case for those diagnosed with depression before their onset of multiple sclerosis, which suggests that the disease itself is not necessarily the cause of depression, according to the researchers.
Unclear cause and effect
"We cannot determine causality with certainty, but it is interesting to note that the risk of worsening disability was higher even in people who were already depressed before the diagnosis of MS," he says. Stefanie Binzer, researcher at the Department of clinical neuroscience at Karolinska Institutet and corresponding author.
The observed associations can be interpreted in different ways. For example, MS patients with depression are more likely to smoke than non-depressed patients and are more likely to neglect their medication. Depressed people are also less anxious to exercise and a lack of physical activity could lead to faster deterioration. It is also possible that depression and MS have shared pathological mechanisms that enhance each other. In this case, the treatment of depression is a particularly important part of the treatment of MS. More research is needed to determine the causality between depression and worsening of MS.