Many of the cognitive issues experienced by patients with fibromyalgia can be attributed to depression.
That finding comes from the study “The effect of depressive symptoms on cognition in patients with fibromyalgia,” which was published recently in the journal PLOS One.
Fibromyalgia is a chronic disease that is characterized by pain, fatigue, and depression. In addition, several studies have demonstrated that patients with fibromyalgia have cognitive impairment compared to healthy people used as controls in the studies — particularly in regard to working memory processes, attention, executive processes, and processing speed.
Working memory refers to a cognitive process that is responsible for temporarily holding information available for processing. Executive functions are a set of processes that have to do with managing oneself and one’s resources in order to achieve a goal.
Patients with fibromyalgia also frequently display psychiatric symptoms such as depression, anxiety disorder, and sleep dysfunction. Many researchers believe that cognitive dysfunction in patients with fibromyalgia can be attributed to these three psychiatric comorbidities.
Specifically, depression has been shown to lead to severe neuropsychological impairment. In particular, depressed patients show defects in attention, memory, psychomotor speed (physical movement related to conscious cognitive processing), processing speed, and executive function.
Researchers set out to investigate whether cognitive issues in fibromyalgia patients can be explained by other factors associated with fibromyalgia, such as depression, anxiety and sleep dysfunction.
They compared 110 patients with fibromyalgia against 33 patients with depressive disorder and 50 healthy controls with regard to many measures of attention and executive functions. Participants also were asked to complete questionnaires on depression, anxiety, and sleep quality.
As expected, patients with fibromyalgia showed higher levels of depression, anxiety and sleep dysfunction compared to healthy controls. In fact, 86% of participants exhibited depressive symptoms, 68% had significant levels of anxiety and 99% showed poor sleep quality.
Interestingly, patients with fibromyalgia did not differ significantly with respect to depression or anxiety when compared to patients with depression. However, patients with fibromyalgia did have significantly worse quality of sleep.
Moreover, researchers found that short-term and working memory and inattention measures were associated only with symptoms of depression. In other words, these differences did not exist between groups once the results were adjusted for depression.
The authors said “This lack of difference [across groups] in most of the cognitive tests supports our main hypothesis that the differences in cognitive performance between groups could mainly be explained by depression for most cognitive domains.”
However, impairment in selective attention — referring to the process of reacting to certain stimuli selectively when several occur at the same time — was found to be an added effect by both fibromyalgia and depression.
Additionally, impairment in processing speed, cognitive flexibility (mental ability to switch between thinking about multiple concepts), and inhibitory control (a cognitive process that allows an individual to restrain their impulses) were found to be the result of interaction between depression and fibromyalgia.
“All these results suggest that improving emotional symptoms in this population would reduce the impairment of attentional processes even though impairment of cognitive flexibility and inhibition would still remain. Our findings also highlight the importance of clinicians understanding this pattern of cognitive dysfunction in order to provide a specific approach that could be used to address both the emotional and cognitive domains and thus help to improve the cognitive performance of those suffering from fibromyalgia,” the researchers concluded.