Researchers have been working on sorting out the causal direction of multiple sclerosis (MS) and depression. These findings suggest that depression can be a consequences of MS-related disability not the other way around.
Depression affects up to half of people with multiple sclerosis (MS) at some point in their lives. Experts in the field have wondered whether depression can make certain individuals more likely to develop autoimmune diseases such as MS, and some evidence suggests that autoimmune diseases can make depression more severe, resulting in worsened progression of MS, creating a cycle of the depression and MS worsening each other. But there are also research findings that show that preexisting depression symptoms has no effect on ultimate MS severity.
Now, a study published in Scientific Reports found that severe MS symptoms were unlikely caused by depression experienced in the initial stage of MS. These findings suggest that when people with MS start feeling depressed early on, it is related to their disability getting worse over time. In other words, the depression is probably a result of the MS-related disability, not the other way around.
For a group of researchers at the University of London and Royal London Hospital led by Benjamin M. Jacobs learning the importance of early depressive symptoms and determining a causal relationship between the two conditions seemed crucial to accurately assess depression’s role in MS progression.
To determine a causal relationship, the investigators collected data from the UK MS Register, a database that has collected self-reported information on demographics, risk factors, MS-related outcomes, and validated outcomes via an online patient portal since 2011. The investigators extracted Expanded Disability Status Scale (EDSS) scores and Hospital Anxiety and Depression Scale (HADS) from the database, ultimately including patient-reported data on 862 individuals.
The primary outcome involved comparing patients with and without early depression based upon their probability of reaching an EDSS score greater than or equal to 6.0. This benchmark of disease severity is commonly used in MS research and corresponds to requiring a unilateral walking aid (e.g., a cane).
The authors found an interesting trend in their data: After standardizing all EDSS scores, early depressive symptoms were associated with an increased likelihood of eventually reaching an EDSS score of 6.0 or greater. Alone, this would suggest that early development of depression in those with multiple sclerosis presents increase the risk of progressing to severe disease, and ultimately a worse prognosis.
However, the researchers adjusted the data again, this time standardizing the baseline EDSS score. Following this assessment, depression was no longer significantly associated with reaching the 6.0 EDSS benchmark. Overall, this suggests that depression and severe MS symptoms are related, but that the early depressive symptoms are more likely the result of more severe initial MS symptoms than the cause of worsening MS.
This study adds further support for the link between depression and MS severity and highlights the continued importance of treating depression in people with MS.