Fainting may have genetic link, study says
August 7th, 2012
12:40 PM ET

Fainting may have genetic link, study says

Maybe it's the sight of blood, or standing too much, or pain, or scary thoughts - in any of these cases, you might find yourself alert one second and unconscious the next.

About 25% of people will faint during their lifetime. The technical term for fainting, when it happens because of an environmental trigger, is "vasovagal syncope."  The process involves a drop in blood pressure.

A new study in the journal Neurology suggests that there is a genetic component to fainting.

Previously, there had been mixed evidence about the role that genetics plays in the tendency to faint. A recent review of studies suggested that any familial correlation was due to chance.

But this study looks at twins, who share more genetic material than any other two people. Researchers looked at 51 same-sex pairs of twins, where at least one had fainted. These included a mix of monozygous (derived from one egg) and dizygous (derived from two eggs) twins. Monozygous twins are more genetically similar and are sometimes said to be "identical," while dizygous twins are called "fraternal."

Researchers interviewed the twins on the phone with a standardized questionnaire. The results suggested that in the twin pairs, both identical twins were more likely to have fainted than both fraternal twins.

"Twin studies provide very strong evidence of a genetic component and are a classical clinical method to look for evidence of genetic effects. This is backed up by the non-twin family data in our paper," said study co-author Dr. Sam Berkovic, neurologist at the University of Melbourne, Australia, in an e-mail.

The research suggests that there is a strong genetic component in fainting, "making subjects vulnerable to environmental triggers to result in a faint at a particular moment, such as emotional events, stress, sight of blood etc." Berkovic said.

There was no evidence that participants had heart problems or autonomic failure (a nervous system disorder) causing fainting, and no twin pair reported a family history of sudden cardiac death.

It appears that there is a spectrum of fainting causes, the study said. On one side, there's genetic factors, particularly when recurrent and associated with typical triggers. On the other side, there are environmental factors, especially "when infrequent and not associated with typical triggers."

This means that people who are closely related may have a similar tendency to faint, Berkovic said. But keep in mind that the study has several weaknesses.  This was a small study, and the researchers did not perform diagnostic tests to exclude other causes of fainting, such as heart problems and autonomic failure.

The research could help scientists identify the genes underlying a tendency to faint, Berkovic said.

To further explore this topic, there should be genetic studies on large families examining the tendency to faint, he said.

soundoff (25 Responses)
  1. heh

    Its just cuased by an old "play dead" gene still floating around our DNA.

    August 7, 2012 at 14:00 | Report abuse | Reply
    • Beatriz

      I'll be putting up a link shtolry for everyone, but we had a technical glitch that I'm trying to resolve, but the wireless in that area is scarce. I'll post something as soon as I get it fixed. I apologize for the delay!

      October 11, 2012 at 11:44 | Report abuse |
  2. gatecrasher1

    Is there a predominance of this gene in women of African descent? "Oh lawdy I'ma gonna faint!"

    August 7, 2012 at 14:06 | Report abuse | Reply
    • Drewbie

      Not to be confused with, "Elizabeth–this is the big one!"

      August 7, 2012 at 16:26 | Report abuse |
  3. Karl from Scottsdale

    Everything now is a genetic problem. Hey, NO MORE PERSONAL RESPONSIBILITY! "The DNA made me do it"!

    August 7, 2012 at 14:11 | Report abuse | Reply
    • Nicole

      That's stupid, people don't faint to get out of responsibilities, they faint at the sight of blood, for example.

      August 7, 2012 at 14:21 | Report abuse |
    • richwag

      Sheesh, what's this world coming too when people won't take responsibility for their genes???

      August 7, 2012 at 14:35 | Report abuse |
    • Er

      I love jeans

      August 7, 2012 at 16:55 | Report abuse |
    • Chris

      They are not opposites. Knowledge is important to build personal responsibility.
      Knowing a predisposition factor means you can use your personnal responsability to reduce the risks. For example, someone predisposed to obesity would watch their exercise and food intake more than others. Or someone predisposed to breast cancer would get more exams.
      Of course, you could be predisposed to breast cancer, never get screened, develop cancer, forgo treatment, and die from it. That's when your personnal irresponsibility could be blamed. But it would have nothing to do with predisposition.

      August 8, 2012 at 14:13 | Report abuse |
    • KAte

      Really? One should take some on some personal responsibility for fainting?

      August 10, 2012 at 04:06 | Report abuse |
  4. bill

    Wow. I dropped out of HS and just got high. I feel my BP dropping. You mean the same thing that makes a person have high blood pressure could also make them have low? Genotype and phenotype just like my plants. In other words, you have the genes but do you have environment that allows expression or recession? Hey, Karl how long can you hold your breath?
    Your body won't let you for long. And guess what? Yawning is an involuntary response to lack of oxygen when you are not trying to intentionally deplete. Who faints because they want to?

    August 7, 2012 at 14:26 | Report abuse | Reply
  5. Billy

    Thanks rick romero. As someone who faints twice a year, I knew that when I was a child. My mother does, her mother did... You don't need a study to know that!

    August 7, 2012 at 14:39 | Report abuse | Reply
  6. t3chsupport

    No one else in my family does, but I have a tendency to. I seldom go all the way out, and usually just completely go blind for a few moments when I stand up. Sometimes it just happens randomly, I go pale where I sit and just kind of fade out. If it's due to low blood sugar, I also go into a cold sweat.

    I love the people that come on and say 'I have such and such an anecdote about my personal experience, why would anyone do a study!'. So dumb.

    August 7, 2012 at 15:12 | Report abuse | Reply
  7. Bioartchick

    My maternal grandfather and I both had/have the same condition that causes fainting when trauma occurs to the fingers. Its not about blood, but more about the pain. So strange!

    August 7, 2012 at 16:01 | Report abuse | Reply
    • Emma

      OMG, I have also fainted several times at trauma to my fingers (once closed them in a door, another time in a window, once with a weird chemical nail polish). In wonder what connection there is with that.

      August 7, 2012 at 17:40 | Report abuse |
  8. Kasey B.

    My mother, uncle and I all faint randomly. It's doesn't start until you hit puberty. None of us have any similar medical conditions, we are all pretty healthy. We can tell when it's going to happen, so we place ourselves in a safe place, faint and wake up in less than 30 seconds. Usually sweaty after it occurs but feel reborn. It's weird. No one knows why or what causes it but it definitely is genetic.

    August 7, 2012 at 16:15 | Report abuse | Reply
  9. DB

    As if I needed someone to tell me "there may be a genetic link" when my brother, my mother, and grandfather are all very prone to fainting.

    August 7, 2012 at 18:09 | Report abuse | Reply
    • Vladimir

      that 1 in 3 girls were sexually ausbed while 1 in 5 boys were. I think this is bunk. Part of the problem was that by many in the field, unwanted sexual attention is considered abuse when it clearly is not. The other aspect is that feminists are camped in the field and even the feminists who are looking for data will most appreciate the data which supports their viewpoint. We all do that.My bet is that real sexual abuse happens to men and women in roughly equal shares. Sadly.Trey

      October 14, 2012 at 00:47 | Report abuse |
  10. Crazybusy

    I faint every time I pay for a tank of gas.

    August 7, 2012 at 18:11 | Report abuse | Reply
  11. DB

    The only time I ever fainted was when I was having four teeth pulled for orthodontic work. The oral surgeon pulled the first one, stuck it in my face and asked "do you want to keep them?" and that was the last thing I remember until I woke up with a mouth full of gauze. I suspect it may have been deliberate, because I'm sure it's easier to get the teeth out when the patient is unconscious.

    Anyway, as I mentioned in another post, my mother is very prone to fainting...and when she heard I'd fainted, SHE started to feel faint. So the nurse actually made me, the patient, get out of the dentist chair so my mother could lie down and put her feet up! It was all very funny.

    August 7, 2012 at 18:14 | Report abuse | Reply
  12. dmg

    I hope they do figure this out. I was a perfectly healthy women until a year ago. I was fainting 4 to 5 times a day. My blood pressure crashes when i stand up. They have given it several names. Orthostatic intolerance, Neuro cardio syncope, postural orthostatic tachycardia syndrome., vaugel syncope. if its a genetic thing then anyone in my family could end up like me. They still have no idea what caused this to happen to me. i can't hold a job, drive, stand in a line or go any where alone.

    August 8, 2012 at 14:58 | Report abuse | Reply
  13. OvernOut

    Sounds like a condition where a person would not want to drive, especially if there is no warning sign before fainting. One of my kids has epilepsy, she has no warnings of seizures. Even though her seizures are controlled by meds, breakthrough seizures happen and it is too risky for her to drive. Be careful out there!

    August 8, 2012 at 23:08 | Report abuse | Reply
  14. birdgirl249

    After my mother's most recent fainting episode, the doctor said that the cause is probably genetic – something to do with the nervous system I think. She fainted when the eye doctor was talking about eye surgery while the patient is awake. My sister and I both faint at the sight of blood, or just at certain medical talk, especially to do with teeth. Even reading certain things can make me dizzy. My first time fainting was at the sight of a bloody tooth when I was seven, and that was in front of my entire church while I was singing in the choir. It would be lovely if there were more research done about this medical condition so that some treatment could be found.

    August 9, 2012 at 01:17 | Report abuse | Reply
  15. Caroline

    Here is my suggestion– DON'T study any more families ... it is money BETTER SPENT ELSEWHERE!!

    August 9, 2012 at 08:07 | Report abuse | Reply
    • Silvia

      wow your really both in love and sortng.. god bless you both and this is inspiring story you have that should husband and wife need to work on instead file on divorce right.. take care

      October 11, 2012 at 04:29 | Report abuse |

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