Melatonin and MS

Multiple sclerosis (MS) is an autoimmune disorder that, like SAD, has been linked to vitamin D deficiency from lack of sun exposure. Interestingly, recent research suggests that a drop in autumn and winter relapses may be linked to peak melatonin levels, which occurs during these darker months.

Conversely, spikes in relapses occurring during spring and summer — which tend to be less common but do occur — may be related to decreased melatonin levels. The research,8 led by neuroscientist Mauricio Farez at the Dr. Raúl Carrea Institute for Neurological Research, looked at 139 MS patients living in Buenos Aires.

Thirty-two percent of them experienced a reduction in relapses during fall and winter, compared to spring and summer. As reported by Scientific American:9

"Past research has shown that melatonin can have a protective effect against MS and that shift work, which disturbs melatonin production, can increase the risk of developing the disease. According to the authors, this research is one of the first to bring together epidemiological evidence with results from both human cells and animal models ...

[And it] may help to resolve a 'seasonal paradox' — MS flare-ups should decrease during warmer, brighter months when people receive more exposure to sunlight and thus produce more vitamin D, which also has anti-inflammatory properties. But some studies, including this one, show that relapses increase in the spring and summer pointing to the possibility that other environmental factors, such as melatonin levels, are involved."

To test their hypothesis, mice with autoimmune encephalomyelitis (the animal model of MS) received daily injections of melatonin. As a result, clinical symptoms were reduced, and harmful T cells, which are pro-inflammatory, were reduced, whereas regulatory T cells were increased. Similar effects were shown in petri dish experiments. As noted in the featured article:

"Melatonin regulates pathways central to the immune response, so these results may pertain to other autoimmune diseases, particularly where seasonal flare-ups occur, such as lupus and rheumatoid arthritis ..."

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