Possible causes of MND (including familial MND)

Sporadic MND

Most people who develop MND have 'sporadic' MND - this means there is no family history, and it is extremely unlikely to develop in other family members. (See below for familial or inherited MND). Little is known about what causes sporadic MND. Several possible factors have been suggested, including exposure to chemicals, fractures and injuries, smoking, military service, and engaging in some sports or high levels of exercise, but research studies have so far failed to find clear conclusive evidence. Probably lots of different factors are involved, and in any one person MND is likely to occur for complex reasons, rather than there being any single cause. Several factors may increase the risk of developing MND or may help to 'trigger' it, but may not be enough in themselves to cause it. The MND Association has summarised the research evidence at: www.mndassociation.org/research/research_explained/

Some people we talked to felt there was little point worrying about what had caused their condition or whether they had done something to cause it. Lots of people asked themselves 'Why me?' but at the same time many felt it was important that people should not blame themselves. Some also pointed out that it would not make any difference to their condition even if they did know what caused it. 

Not even the experts know why people get MND. She knows there's no point worrying if she did something to cause it, but sometimes she can't help it.

He wonders if giving up smoking after 50 years had anything to do with getting MND but his consultant reassures him it's nothing he's done.

Not knowing what had caused their condition was frustrating for some people. While some could live with the idea that it was just chance, others struggled with this idea, especially if they and their families had always been very fit and healthy. 

He can't understand why both he and his wife developed MND. He thought playing a lot of sport might have had something to with it in his case.

Some had done a lot of reading and searching on the internet for different theories about causes and the latest research evidence. 

He has read up on lots of different causes. He worked in farming and wonders whether exposure to sheep dip affected him, or whether it's just chance.

People mentioned a wide variety of what they thought might be possible risk factors from their own experience, including:

• A stressful lifestyle or particularly stressful events
• Diet
• Exposure to chemicals (especially in agricultural work and on food, but also when working as a firefighter and installing industrial machinery)
• Exercise, sport and sports injuries
• Other injury (including head injuries and leg injuries)
• Previous chemotherapy and surgery
• Medication for depression
• Amalgam teeth fillings
• Throat infections, viruses
• Lyme disease
• Genetics
• Frequent travelling (including muscle cramps caused by sitting still for long periods).

She has thought of many things which might have caused her MND including injury, stress, dental fillings and crop-spraying near her house. [Voice software interview].

They wonder if exposure to chemicals in farming or Mike's days as a firefighter might have caused MND, including during the foot and mouth outbreak. [Mike is unable to speak].

He has thought about lots of possible causes. He has spent time near laundry chemicals, but not as much time as the laundry workers themselves.

He believes Lyme Disease may trigger MND, and sometimes may be mistaken for MND, but British doctors are much less aware of Lyme Disease than doctors in other countries.

Some people thought there was evidence of a cluster of cases where they lived, including a woman who knew of three people with the condition using the same hairdresser. 

She wonders if hairdressing products might have caused a cluster locally, but it seems unlikely. She also wonders about the effects of stress and pesticides on fruit.

As several people commented, understanding the causes could help in finding a cure, and some were frustrated by what they saw as the lack of progress in research. 

Searching for a cause helps people cope with MND, but it can become an obsession. She would like to see more research into the effects of crop-spraying. [Voice software interview].

More funding and more research are needed for MND. He believes all new patients should be routinely asked questions about their lifestyle, to help identify causes or triggers.

The MND Association website provides a list of trial in progress and any results available so far at www.mndassociation.org/research/research_explained/treatment_trials.html

Information about how to get involved in research, including the MND Association DNA bank and national database can be found at www.mndassociation.org/research/research_explained/

Familial or inherited MND

In 5-10% of cases MND runs in families; in about 20% of these families a particular gene carrying mutations has been identified, the SOD-1 gene (superoxide dismutase). Some people we talked to who had younger children worried especially about whether their MND might be an inherited form and some had been tested to check if they had an SOD-1 gene mutation.

The age at which symptoms first appear, type of onset and speed of progression can vary as much from person to person in familial MND as they can in sporadic MND. For some people, their own diagnosis may be the first time anyone has suspected a family connection, and it may not be immediately obvious if they have different symptoms. (See Interview 34 - Ken's story). A woman diagnosed in her thirties had known for some years she was at risk but assumed that if she did get MND it would be later in life, like her father and uncle. 

She had already met her future husband at university before her father died of MND. They assumed it was unlikely to affect her until she was much older.

Knowing that MND runs in the family raises particular issues for people about whether they themselves will get the condition, and whether their children and other family members will also get the condition.

Her father did not have the SOD-1 mutation so she did not have genetic testing. She had already been diagnosed before she and her husband would have thought about having children.

She might not have had children if she'd known she had familial MND, but she's glad she has them. She wants them to have positive memories of her life with MND.

So far her children have decided not to be tested for the SOD-1 gene mutation. At the moment neither of them wants children.