Does Head Injury affect your risk of MS...apparently it can

Montgomery S, Hiyoshi A, Burkill S, Alfredsson L, Bahmanyar S, Olsson T.Concussion in adolescence and risk of multiple sclerosis.
Ann Neurol. 2017 Sep 4. doi: 10.1002/ana.25036. [Epub ahead of print]

OBJECTIVE:To assess whether concussion in childhood or adolescence is associated with subsequent multiple sclerosis risk. Previous research suggests an association but methodological limitations included retrospective data collection and small study populations.
METHODS: The national Swedish Patient (hospital diagnoses) and Multiple Sclerosis registers were used to identify all MS diagnoses up to 2012 among people born from 1964, when the Patient Register was established. The 7292 patients with multiple sclerosis were matched individually with 10 people without MS by sex, year of birth, age/vital status at multiple sclerosis diagnosis, and region of residence (county), resulting in a study population of 80212. Diagnoses of concussion and control diagnoses of broken limb bones were identified using the Patient Register from birth to age 10 years or from ages 11 to 20 years. Conditional logistic regression was used to examine associations with multiple sclerosis.
RESULTS:Concussion in adolescence was associated with a raised risk of multiple sclerosis, producing adjusted odds ratios (and 95% confidence intervals) of 1.22 (1.05-1.42, p=0.008) and 2.33 (1.35-4.04, p=0.002) for one diagnosis of concussion, or more than one diagnosis of concussion, respectively, compared with none. No notable association with multiple sclerosis was observed for concussion in childhood, or broken limb bones in childhood and adolescence.
INTERPRETATION: Head trauma in adolescence, particularly if repeated, is associated with a raised risk of future multiple sclerosis, possibly due to initiation of an autoimmune process in the central nervous system. This further emphasises the importance of protecting young people from head injuries.

I am sure some of you will be interested in this that head injuries to the state of concussion doubles the risk of subsequently developing MS  Do head injuries cause MS I doubt it or the risk factor would be higher. So head injury is like smoking, except you can not smoke out of choice.