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Twenty-year data from the Nurses’ Health Study (NHS) suggests that depression is associated with a 2-fold increased frequency of systemic lupus erythematosus (SLE) - the question is why?
An analysis of 194,483 women in the NHS sought to identify incident SLE cases meeting ACR criteria (with 4 or more criteria) bases on self-report and confirmed by medical record review. Depression was based on a clinician’s diagnosis of depression, antidepressant use, or a score of less than 60 on the 5-item Mental Health Inventory (MHI-5).
Among from 194 483 women (28-93 years of age) in the NHS, there were 145 incident cases of SLE.
Women with depression had over a 2 fold increased risk of SLE (HR, 2.67; 95% CI, 1.91-3.75; P < .001) compared to those with no depression. This risk was largely unchanged after adjustment for body mass index, cigarette smoking, and oral contraception and postmenopausal hormone use.
The Lupus risk was evident regardless of the measure used to establish depression - clinician’s diagnosis, antidepressant use or MHI-5 scores.
Why would depression may be associated with increased risk of SLE remains unclear. Depression may occur as part of a neuropsychiatric manifestation of lupus. Some research indicates immunologic abnormalities in those with depression and patients with depression have a slightly higher rate of autoantibodies.
Limitations of the NHS and this kind of research are several. First, nurses who are enrolled may not be truly representative of the population, as nurses tend to be more more homogeneous as a group and tend to be generally white, thinner, more health-conscious, highly educated. Moreover this comes with the limitations of an observational study. Hence these findings are best at generating hypotheses that can be further studied with intervention and other forms of randomized trials.