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Medicine Science

Cat Parasite May Increase Risk of Suicide In Humans 252

An anonymous reader writes "Researchers at the University of Maryland analyzing meticulous data collected by Danish authorities have identified a positive correlation between suicides among women with infection with the fairly common parasite T. gondii. Carriers were 53 percent more likely to commit suicide in a sample of 45,000 Danish women monitored for over a decade (researchers believe that the same correlation likely exists for men). Increased susceptibility to schizophrenia and bipolar disorder was also discovered. The physiological mechanism has not been determined, although some speculation centers around changes to dopamine levels. Two intriguing aspects were noted: 1) human infection often (but not always) begins by exposure to cats carrying the parasite, for example, by changing an infected animal's litter; and 2) the parasite spreads itself by infecting the nervous system of rodents, causing them to become suicidally attracted to feline odors which will increase the likelihood of their hosts being eaten by cats, whose digestive tracts provide the preferred environment for parasite reproduction."
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Cat Parasite May Increase Risk of Suicide In Humans

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  • by pyzondar ( 1234980 ) on Sunday July 08, 2012 @05:20PM (#40585315)
    Do the crazy cat ladies have cats because they are crazy, or are they crazy because they have cats?
  • by Anonymous Coward on Sunday July 08, 2012 @05:42PM (#40585503)
    Exactly. Also:

    2) the parasite spreads itself by infecting the nervous system of rodents, causing them to become suicidally attracted to feline odors

    Suicidally? Being attracted to something known to shorten your lifespan doesn't mean you're suicidal. Take one example: Americans gorging themselves on McDonald's, then flooding hospitals with heart disease cases in an attempt to stay alive. If they were suicidal, they'd just keep eating more burgers and look emo about it till they died.

  • by girlintraining ( 1395911 ) on Sunday July 08, 2012 @05:43PM (#40585511)

    Do the crazy cat ladies have cats because they are crazy, or are they crazy because they have cats?

    The parasite also causes decreased sexual inhibition. Translation: It makes women sluttier. No corresponding effect was found in men. Of course, this effect isn't as widely documented for obvious political reasons...

  • by AK Marc ( 707885 ) on Sunday July 08, 2012 @05:59PM (#40585629)
    A 50% increase is statistically significant, but in absolute numbers wouldn't make that much of a difference, certainly well under the "killed by cars" number, and we don't care enough about that to actually fix the problem.

    What I see out of this, and others like it, is that there are a large number of diseases we get infected with over our lives that never leave us, and have effects well into our old age. We wouldn't have "evolved" out of them because the evolutionary pressure for things that don't affect us until after we've passed on our genes is small and indirect. How many "diseases" and infections do we have by the time we are die? What would our old age be like if we managed to avoid/cure them all?
  • Re:Terrorist Weapon? (Score:1, Interesting)

    by znrt ( 2424692 ) on Sunday July 08, 2012 @06:44PM (#40585941)

    methinks it was irony. it made me smile, anyway.
    because it's not completely unbelievable that some fuctard in some govt office or news show eventually dished out such and idiotic thought to fuel the turrsts panic story. in fact, it's a very accurate caricature. bitter, if you like, but caricatures often are.

  • by Harvey Manfrenjenson ( 1610637 ) on Sunday July 08, 2012 @07:26PM (#40586279)

    The Danish study is just the latest in a long series of studies which demonstrate a correlation between toxoplasmosis seropositivity and psychiatric problems-- it's been linked to schizophrenia and ADHD, and so on. Wikipedia has a good article on the topic.

    It's pretty interesting. Apparently something like 10% of the US population is seropositive for toxo. The infection is thought to be "contained" immunologically, but encysted organisms are still present in muscle and nervous tissue, and the process of "containment" may induce a subtle inflammatory state which affects a broad variety of neurotransmitters (not just dopamine). It's also possible that the causation works the other way-- the people who get chronic infections may have something about their immune system that is different to begin with, and the difference might predispose them to psychiatric problems independently of toxo infection. Good discussion of all that in the Danish study, which was published in Archives of General Psych and seems to be non-paywalled.

    What will be really interesting is to see what happens if you identify psychiatric patients with chronic toxo and try to eradicate the toxo with antibiotics-- do their psych symptoms improve? There have been at least two studies I could find (one where it helped and one where it didn't), and apparently there's a large-scale study getting started in the UK.

  • Control group (Score:5, Interesting)

    by phantomfive ( 622387 ) on Sunday July 08, 2012 @07:35PM (#40586341) Journal
    For people who are wondering, it looks like they didn't have a good control group. So here is how they answered some potential objections:

    1) What if depressed people get cats, and that's why they have the parasite? Did they check people who have cats but aren't depressed?
    It's probably not related to cats, because most people who get this parasite get it from undercooked meat.

    2) What if depressed people are more susceptible to this parasite because they are depressed? What if non-depressed people are capable of fighting off the parasite with a stronger immune system?
    There was no correlation between people who had the parasite, and people who had a history of mental illness. (Also, correlates with other studies, that might have had better control groups, I'm too lazy to check them out to see).
  • by stephanruby ( 542433 ) on Sunday July 08, 2012 @07:42PM (#40586397)

    You seem to know about this field. Can you translate this part for me?

    Separate logistic regression for RhD-negative subjects showed a 2.53 times higher risk of traffic accidents in Toxoplasma-infected than Toxoplasma-free subjects (CI95: 1.12–5.7, t = 2.23, P = 0.026). http://www.biomedcentral.com/1471-2334/9/72 [biomedcentral.com]

    Are they really saying that this is causing "2.53 times higher risk of traffic accidents" among their infected population of Czech male military draftees???

    Imagine the repercussions if this is found to be also true in other populations (not that it will be, and not that correlation equals causation, but...):

    Car Insurance rates (or driver licenses) could start depending on the results of those blood tests. Criminal sentencing could be affected by the results of those tests. And at the very minimum, the next time you'd fill out a questionnaire for getting car insurance, or filling out an application for becoming a truck driver or operating heavy machinery, or applying to get into the military, you'd be asked all kinds of questions about your history with cats (whether you owned one, your significant other owned one, or whether your family ever owned one while you were growing up).

  • Re:Terrorist Weapon? (Score:2, Interesting)

    by dimeglio ( 456244 ) on Sunday July 08, 2012 @08:49PM (#40586913)

    In some countries, the period is used to separate 1000's and the comma is the "decimal" point. Thus, 10,000 dollars would be 10.000,00

  • by LordLimecat ( 1103839 ) on Sunday July 08, 2012 @09:44PM (#40587245)

    Guilt about sex is one of the things religion uses to keep people in line.

    Except for the whole book of Song of Solomon, you mean.

    But dont let your ignorance get in the way of your anti-religious sentiment, this is slashdot and theres karma to be had.

  • Re:I have 7 cats (Score:3, Interesting)

    by BluBrick ( 1924 ) <blubrick@NosPaM.gmail.com> on Monday July 09, 2012 @01:10AM (#40588503) Homepage
    Maybe Toxoplasma gondii merely causes its hosts to engage in higher risk behaviours. In the wild, for small prey animals such as rats and mice, that is likely to be lethal and result in being eaten by a suitable carrier, but in this artificial environment we live in, perhaps it manifests in other ways. For example, flouting controlled substance laws to gamble 20-30 IQ points against a little temporary euphoria - then bragging about it - that sort of thing.
  • Bullstuff (Score:1, Interesting)

    by norteo ( 779244 ) on Monday July 09, 2012 @02:57AM (#40588905)
    I am an aerospace engineer. If aircrafts where built with the rigorousity this study was done, every aircraft would crash.

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