Ruth AnnMarrie, Neurologist, University of Manitoba
ChristianeWhitehouse, Graduate student, Dalhousie University
JohnFisk, Neuropsychologist, Dalhousie University
Published February 21, 2019
We thank Dr. Golan for the comment on our article.1 We agree that immune-mediated inflammatory disease (IMID) activity and severity are associated with anxiety but disagree with the conclusion drawn. In longitudinal studies, we have shown that psychiatric comorbidity is associated with greater multiple sclerosis–related disability progression over time.2 Similarly, in inflammatory bowel disease (IBD), elevated symptoms of anxiety at baseline are associated with a shorter time to recurrence of clinical IBD symptoms.3 Therefore, IMID severity or disease activity would fall in the causal pathway between anxiety and cognition, and should not be treated as confounders, because this would create overadjustment bias.4 In the general population, anxiety is known to adversely affect cognition. This is consistent with findings among our study participants who had depression or anxiety, but who did not have an IMID. Moreover, the strength of the association between anxiety and cognition was the same across all groups. Collectively, these observations indicate that the reported association between anxiety and cognition is not solely explained by unmeasured confounding.
References
Whitehouse C, Fisk J, Bernstein C, et al. Comorbid anxiety, depression, and cognition in MS and other immune-mediated disorders. Neurology 2019;92:e406–e417.
McKay KA, Tremlett H, Fisk JD, et al. Psychiatric Comorbidity Is Associated with Disability Progression in Multiple Sclerosis. Neurology 2018;90:e1316–e1323.
Mikocka-Walus A, Pittet V, Rossel JB, von Kanel R. Symptoms of depression and anxiety are independently associated with clinical recurrence of inflammatory bowel disease. Clin Gastroenterol Hepatol 2016;14:829–835.
Schisterman EF, Cole SR, Platt RW. Overadjustment bias and unnecessary adjustment in epidemiologic studies. Epidemiology 2009;20:488–495.
We thank Dr. Golan for the comment on our article.1 We agree that immune-mediated inflammatory disease (IMID) activity and severity are associated with anxiety but disagree with the conclusion drawn. In longitudinal studies, we have shown that psychiatric comorbidity is associated with greater multiple sclerosis–related disability progression over time.2 Similarly, in inflammatory bowel disease (IBD), elevated symptoms of anxiety at baseline are associated with a shorter time to recurrence of clinical IBD symptoms.3 Therefore, IMID severity or disease activity would fall in the causal pathway between anxiety and cognition, and should not be treated as confounders, because this would create overadjustment bias.4 In the general population, anxiety is known to adversely affect cognition. This is consistent with findings among our study participants who had depression or anxiety, but who did not have an IMID. Moreover, the strength of the association between anxiety and cognition was the same across all groups. Collectively, these observations indicate that the reported association between anxiety and cognition is not solely explained by unmeasured confounding.
References
Footnote
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