Mental illness is certainly an important aspect of many of our patients’ struggles, and I hope I’ve made the case earlier that it’s something pediatric rheumatologists should be paying attention to… There is a lot of good literature to show that patients with chronic disease, in general, are at higher risk for mental illness.
This makes sense to me, conceptually, that children and adolescents burdened with the stress and chaos of illness are at risk for psychological distress. Physical illness begets mental illness. I can also understand that this can be a bi-directional relationship, in which mental illness can in turn make physical illness worse. Perhaps this occurs in our patients when they are depressed if they are less likely to see their PCPs, or take their medications, or perhaps, as some have suggested, there are neuro-inflammatory effects that the brain has on the body that worsen physical inflammatory disease. But can mental illness cause inflammatory disease?
The authors of an article that recently came out in PLOS ONE suggest, yes. Specifically they suggest that affective disorders such as Major Depressive Disorder can cause arthritis in adolescents.
The article, more generally, is about links between mental and physical comorbidities, in which Tegethoff and her colleagues examined data from the Adolescent Supplement of the National Comorbidity Survey. In this survey, data was collected on demographics, mental illness, physical illness, and the reported timing of those.
The group previously published data showing associations between 5 different categories of mental illness and 8 different physical illnesses, in which there was a significant association between arthritis and mental illness, most notably anxiety (but also some association with affective disorder and substance abuse). In their most recent study, they examined timing to try to determine the direction of these associations. In terms of statistical significance and effect size, one of the most remarkable findings was the association of previous affective disorders with the development of arthritis, for which the hazard ratio was >3. In contrast, no significant hazard ratios were found the other way round, in terms of arthritis predicting mental illness.
While we’re cogitating on this, let’s review some important limitations to this study:
1) The presence and timing of physical illness was defined by a questionnaire administered to adolescent participants. The authors argue that this is a valid way of determining diagnosis, and they cite evidence showing that children are just as reliable as adults in describing their illness experience and health status. Perhaps one can use this to argue that they will be just as good at reporting physician-given diagnoses, but as one of their citations found, even in adults self-reported diagnoses agree well with physician diagnoses, except in the case of arthritis!
2) This brings up the question of how people interpret ‘arthritis’ (which is exactly as specific a terminology as was used in this study’s questionnaire ). To a rheumatologist this has a specific meaning and does not include joint pain without other findings, to a patient or even another researcher, this may be different. The US National Health Interview Survey used by the CDC collects data on arthritis with the following question: “Have you EVER been told by a doctor or other health professional that you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?”
Is it possible then, that the number of participants with JIA and other forms of chronic arthritis (what I thought of when I read “arthritis”) were few among this sample? And that others with joint pain or chronic pain syndromes were included and even drowned them out?
Looking at the authors’ previous paper about 2% of the total sample reported having had arthritis. This is at least 14 times what we would expect for the prevalence of chronic arthritis. On the other hand, juvenile fibromyalgia may be as prevalent as 6% and non-specific joint pain, more than that. Perhaps what is truly being observed here is the temporal relationship between affective disorders and musculoskeletal pain. This would be much less surprising and is congruent with all we know about amplified musculoskeletal pain syndromes, fibromyalgia, and their associations with mental illness.
So in my mind, the question of whether mental illness can cause chronic arthritis, whether JIA, lupus, or other, is still unanswered… but is it a far-fetched hypothesis? Certainly hypotheses that stress contributes to the development of autoimmune or inflammatory disease are not new, so perhaps this area is worthy of further research.
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