Do left handers get more migraines?

I read an article the other day about a study that claimed left handers ran several times the risk of suffering from migraines as their right-handed counterparts. This was because they found there was a higher frequency of left-handedness in patients who suffered from migraines than in their control groups.

Interesting finding, but why should that be?

I then read that another study, done by scientists in Germany, found there was no evidence at all to suggest we southpaws are more prone to migraines.

So how are we supposed to know what to believe when we read such articles? My anecdotal evidence is that the people I know who suffer from migraines are all right handed.

Left-handed Stone Age men

I read something interesting the other day: there is evidence that lefthandedness was fairly common in the Stone Age. University researchers looked at 507 hand prints in 26 caves in France and Spain that were painted between 10,000 and 30,000 years ago.

They found that 23% were prints of right hands, indicating that they were made by left handers - as they would have painted the cave wall using their left hand and done the print with their non painting hand. Today, only about 12% of us are lefties.

But, then I've also read that tools found in Stone Age times were sharpened equally for left and right hand use, suggesting left handedness was far more prevalent than 23%. So who knows what to believe?

What makes us left handed?

On last Friday’s blog, I mentioned that around 10%-12% of the population is left handed. But what exactly determines which is our dominant hand? It’s not exactly known, but here are a few theories:

• A number of studies have shown that left handedness is genetic. So, if both your parents are left handed, there’s about a 50:50 chance that you will be as well. If one of your parents is left handed there’s a 20% chance you will be and if both your parents are right handed, there’s only a 2% chance that you’ll be a lefty.

• Prematurely-born babies and those with a low birth weight have a greater propensity to being left handed. This could be due to brain damage to the left hemisphere of the brain which means the right hemisphere becomes the dominant side.

• Another reason is when the mother produces high levels of the male hormone, testosterone, and passes this to her unborn child. This could be why there are more left-handed males than females.

• Left handedness occurs more frequently in identical twins. However, they aren’t usually both left handed. You’ll tend to find that, where one is left handed, the other will be right handed.

• There was a study done in Canada which showed that women aged 40+ are more than twice as likely to give birth to left-handed babies as younger mothers. This could be because older mothers are more likely to have birth complications.

Whatever the reason for left handedness, those of us who are ‘southpaws’ feel we are part of some special ‘club’. Somehow different and, of course, special. :)