Multiple Sclerosis: Nature, Nurture, or Something Else?

Neuroscience_Neurology.jpgMultiple sclerosis (MS) is a poorly understood disease that affects patients at an early age and, usually, lasts a lifetime. Factors that predispose to the development of MS include genetics, geographic location, sex and birth month, suggesting an interesting nature-nurture interaction in this disease process.

The increased rate of MS at high latitudes has been demonstrated in many studies, with those living in the Northern United States and Canada at a higher risk than those closer to the equator. This geographical influence is most commonly linked to the decreased (UV) radiation in these locations. UV light is a requirement for the production of vitamin D, and it is this effect that is most commonly thought to increase the risk of MS. In addition to affecting bone strength, vitamin D interacts with over 1,000 intracellular pathways, most of which are not well understood. Vitamin D deficiency is documented in patients living at higher latitudes, where MS is more prevalent. Conversely, individuals who work outdoors and have increased sun exposure show a decreased prevalence of MS. Interestingly, the effect of latitude on MS risk is most prominent in infancy in childhood — meaning that moving to an equatorial climate later in life is of limited benefit.

SunHowever, a direct link to early childhood vitamin D deficiency and development of MS is lacking, and there are other factors that may cause the same geographical effects. In North America, people of Scandinavian descent are concentrated in the Northern and Western areas, which are the exact locations with the highest MS rates. This suggests the possibility that genetics, in addition to environment, play an important role. Some studies have found South Asian immigrants to Northern climates to have no increased risk of MS, while others find they, or their offspring, to have increased rates of the disease. British migrants to Africa have lower rates than their counterparts who remain in the UK. Clearly there is some interplay between genetic and environmental factors.

There is seasonal variation in the development of MS, based on birth month. Infants born in May have the highest risk, while those born in November have the lowest. This phenomenon may also be explained by exposure to UV light. Women who are pregnant during the winter, and giving birth in late spring, have decrease sunlight exposure compared to those who are pregnant during summer months, suggesting beneficial effects of UV exposure in utero (womb).

Inheritable factors are also present — monozygotic (identical) twins show a higher concordance rate of the disease than non-twin siblings and unrelated persons. In addition to genetic and geographic factors, certain viruses, smoking and female sex are also associated with increased risk of MS.

Clearly we are far from understanding this disease. MS has a variety of seemingly independent factors associated with its development. In addition to the usual suspects — genetics, sex and poor health habits such as smoking — MS is also linked to what appear to be unrelated and uncontrollable factors such as birth place and birth month. The true link underlying all of these factors is currently unknown, but when it is ultimately identified may provide key insights into the pathogenesis and potential treatment pathways of this poorly understood disease.


EBERS, G. (2008). Environmental factors and multiple sclerosis. The Lancet Neurology, 7(3), 268-277. DOI: 10.1016/S1474-4422(08)70042-5

  • Ellen Lerner

    In other words, no one knows for sure the link between MS and proposed theories of causes. What seems possibly the cause for some may not prove to be true for others. The statistics show similarities but there are individual differences which don’t necessarily fit the statistical model. Some diseases occur seemingly spontaneously maybe from a genetic change or new virus or something in the environment- something that did not exist in a family or person before? could MS be one of those?

  • Dear Ellen,

    Thanks for your commentary. I suggest that you read an interesting review article (free and open access) published in the International MS Journal that discusses the potential link between the herpes viruses and MS as potential players in the disease process.

    In brief, here are their summary points:

    • Human herpesviruses (HHV) may be key players in the MS disease process.
    • There is evidence that HHV may interact with, or activate, human endogenous retroviruses. HHV also infect central nervous system cells, which may have cytopathic effects.
    • Herpes simplex virus, varicella zoster virus, human herpesvirus-6 and Epstein–Barr virus are consistently linked with MS: with epidemiology, with antibody responses (serum and/or cerebrospinal fluid) and with virus-associated MS exacerbations.
    • Although antiherpes medications have shown only minor effects in treating MS, we should not overlook the fact that beta interferon is an antiviral compound that affects both retroviruses and herpesviruses.

    Thank you.



    Christensen T. Human Herpesviruses in MS. Int MS J. 2007 Jun;14(2):41-7.

  • New Zealand is getting over 5 hours of direct sunlight daily. However, Multiple Sclerosis is widespread in NZ.

    At the same time NZ is highly polluted with all sorts of man-made chemicals of all sorts (especially different pesticides).

    Al these chemicals are well known as immunotoxins and neurotoxins.

    I was diagnosed with MS after 6 months exposure to different organic solvents etc. Sadly, it was enough to develop an autoimmune response

    Dr. Czes Kulvis

  • Tom

    My mother is currently going through a bunch of tests for MS to see if she has it or not. One of the questions they’re trying to figure out is if brain disease and MS have anemia as a symptom? Does anyone know if that is the case or not!?

  • Graham Betts

    Did anybody find out what the prevelance is of people that have M.S. if they also earlier had mono, or Epstien-Barr, chicken pox or any disease that resulted from HSV 6 virus?

  • verna

    The increase of defiency in Vitamin D and therefore the inability to absorb calcium seems to be worldwide. MS. Autism ,dementia, and upper respritory related deaths and illness is also on the increase. I have zero vitmin D and cannot absorb calium. I am in constant pain and it is becoming debilitating.I have been researching the Strataspheric Aerosol Geoengineering and Solar radiation management programs that are underway. The sun is be blocked folks. According to what I have been reading at least 25% of the suns rays nolonger hit our planet. All Man manipulated by those with enough money. Our Weather is being taken over. The jet stream being diverted, the Ionosphere being raised, Our atmosphere is nolonger nuetral ,they are conductive. The Aluminum, barium, srontium and other heavy metals and nanoparticulates used in these “field studies” ,and that being our atmoshere. Its being used as a lab and we are the lab rats. Thus all the problems in increased health issues stated above are directly being affected if not totally the cause. I am mad as hell over this, it has destroyed my physical health.Please look into these matters. I am calling on anyone in the postion of authority to help us end this crime against humanity and are planet. Verna

Lindsey Kay, MD

Lindsey Kay, MD, is a medical doctor with training in pathology, and an avid writer. During his training, he worked on pre-clinical and clinical trials in a variety of laboratories related to alcohol effects on the brain, cancer diagnosis, and alternative medicine.

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