Patients in the early stages of multiple sclerosis with mild to moderate symptoms of depression performed worse on cognitive tests related to multitasking than on those focused on single tasks, a study has found.
Notably, no such association was observed among healthy individuals, suggesting an MS-related link between mood, or depression symptoms, and multitasking — when a person’s attention is divided across more than one task at a time.
These findings also highlight the importance of assessing MS patients’ multitasking abilities, as traditional cognitive tests, which typically evaluate how a patient performs on a single task, may miss cognitive changes related to depression.
Still, further studies are needed to clarify how depression and cognition affect each other and identify its underlying biological mechanisms, which may help in the development of effective treatments for mood and cognition in MS, according to the researchers.
The study, “Depression and cognitive function in early multiple sclerosis: Multitasking is more sensitive than traditional assessments,” was published in the Multiple Sclerosis Journal.
Depression and cognitive deficits are common symptoms of MS. Increasing evidence suggests a link between depression and worse attention span and executive function — the set of cognitive processes necessary for planning, focusing attention, remembering, and multitasking.
Cognitive tests used in MS “do not adequately assess executive control of attention, but instead focus on cognitive speed during monotasking demands,” the researchers wrote.
This may help explain why MS patients with symptoms of depression “often perform normally on objective cognitive tests despite cognitive complaints in everyday life,” the team wrote, adding that “cognitive difficulties may emerge in naturalistic settings with distractions and demands for flexible control of attention across multiple responsibilities (i.e. multitasking).”
The researchers, from Icahn School of Medicine at Mount Sinai in New York, set out to better understand the link between depression symptoms and cognitive monotasking (i.e., performing a single task) and multitasking in early MS.
They examined depression and cognitive data from 185 people diagnosed with relapsing-remitting MS (RRMS) or clinically isolated syndrome in the previous five years and from 50 healthy individuals who served as controls.
MS patients (132 women and 62 men) were part of the National Institutes of Health-funded prospective RADIEMS study, designed to evaluate risk and protective factors for cognitive decline in early MS.
The patients’ mean age was 34.4 years, and 89.2% had RRMS. There were no significant demographic differences between people with MS and healthy participants.
In addition to completing a battery of standard monotasking cognitive tests (four for cognitive efficiency or speed and four for memory), MS patients and controls completed a multitasking assessment where they were asked to maintain attention on both a visual decision speed task and a separate auditory attention task at the same time.
Depression was assessed with two self-reported questionnaires: the Beck Depression Inventory-Fast Screen (BDI-FS) and the Mental Health Inventory-5 (MHI-5). Based on BDI-FS cutoff scores, 71.4% of MS patients had no to minimal depression, while 28.6% showed mild to moderate depression.
Results showed that mild to moderate depression among MS patients was significantly more associated with worse ability to multitask than with changes in other cognitive monotasking outcomes, with more depressive patients showing a greater decline in multitasking than in monotasking performance.
The link between depression and multitasking was more than three times stronger than that between depression and the individual visual decision speed task, which “highlights multitasking as driving the relationship to depression,” the researchers wrote.
Similar associations were seen when depression levels in MS patients were assessed with the MHI-5. Data also showed that depression symptoms were more strongly linked to problems in cognitive efficiency (speed) than in memory.
Further analysis indicated that the association between depression and cognition was independent of patients’ disease burden — as assessed through brain lesions and brain volume in MRI scans.
In addition, there were no links between depression (BDI-FS or MHI-5) and multitasking among healthy controls, who had significantly fewer depressive symptoms and better multitasking performance than MS patients.
Notably, multitasking performance between the two groups was no longer significantly different when adjusted for depression, suggesting that depression could partially explain these differences in the ability to multitask. However, studies involving more healthy individuals are needed to confirm this, the team noted.
These findings suggest that discussing cognition and depression in MS patients as separate entities “may be artificial and lead to over-simplification of related processes that may share underlying neural bases,” the researchers wrote.
“It is possible that depression negatively impacts cognition or that depressed mood is a reaction to reduced quality of life related to cognitive deficits,” the team wrote, noting that poor attention control (whether due to disease and/or poor mood) may also be contributing to both.
Future research is therefore needed to clarify the direction of this link, and RADIEMS’ planned three-year follow-up may help with this, the team noted. Still, further studies are also needed to identify the mechanisms behind this link between depression and cognition in MS patients.
“It is important for future research to be guided by lessons from cognitive and affective neuroscience to build biologically plausible models of how the neuroinflammatory and neurodegenerative disease of MS mediates links between mood and cognition, determine whether these differ across patients, and develop evidence-based treatments for mood and cognition in MS,” the researchers concluded.
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