Pharyngula

Genetic link of OCD explored (student post)

Researchers at Cambridge conducted a study that measured cognitive function and analyzed images of the brain in individuals with obsessive compulsive disorder (OCD). Magnetic resonance imaging (MRI) was used to capture images of each participants’ brain, and computerized tests were given to study the ability of the individual to stop repetitive behaviors. Also included in the study were healthy family members of the individuals with OCD, and healthy, unrelated individuals used as a control. The family members were included so that the genetic link behind OCD could be explored.

The researchers discovered that individuals with OCD and their relatives did worse on the computerized tasks than the healthy control group. When the MRI photos were analyzed, individuals with OCD and their relatives were found to have distinct patterns in their brain structure, namely a decrease in grey matter in brain regions associated with the suppression of responses and habits.

It was noted that this decrease in grey matter may contribute to the characteristic compulsive and repetitive behaviors associated with OCD. However, researchers are still a long way from discovering the genes involved with OCD, and further research needs to be done to explore why some family members with the altered brain structure do not develop OCD.

Since the family members have similar brain structure, there must be something else contributing to the development of OCD. I wonder if there is something going on inside that is causing a chemical imbalance that contributes to OCD, or if environmental factors are important in the development of OCD. It would be interesting to look at identical twins and see what the pattern of OCD is in them.

Comments

  1. #1 Ryan
    November 27, 2007

    Hi PZ!

    I just got the third part of my “Evolution for Creationists” series posted. This one discusses atavisms and endogenous retroviruses. See it here:

    http://aigbusted.blogspot.com

    -Ryan

  2. #2 Jackie
    November 27, 2007

    Thanks for the link. This is interesting. I wonder if the difference between those with OCD and those without is the severity of the “decreases of grey matter in brain regions important in suppressing responses and habits.” As Menzies stated in the article, “the current diagnosis of OCD available to psychiatrists is subjective.” The study would suggest that symptoms manifest in varied amouts. Perhaps the decision of whether a patient is diagnosed with OCD ultimately relies on an artificial line drawn between “normal” and “abnormal.”

  3. #3 The Sinaloa Cowboy
    November 27, 2007

    “It would be interesting to look at identical twins and see what the pattern of OCD is in them.”

    If one identical twin has OCD there is an 87% chance the other twin will have it, or a 13% chance he/she will not.

    http://www.ocfoundation.org/ocd-in-children.html

  4. #4 Ken
    November 27, 2007

    Since symptoms can be displayed in varied amounts it would seem to be much more than an on/off situation. Interesting post. PZ, hats off to you for including your students here. They keep bringing us interesting. Keeps my day interesting when moving numbers from one column to another.

  5. #5 Schmeer
    November 27, 2007

    Interesting study. I think I enjoy your posts the most out of all the students.

    I didn’t see any discussion in that article on how many subjects there were and how the control group was selected. I was wondering if the difference between poor perfomance of the related subjects and the comparatively better control could be chance?

  6. #6 Alison
    November 27, 2007

    It would also be interesting to see if the OCD subjects were diagnosed with that alone, or had other comorbid conditions.

  7. #7 Sili
    November 27, 2007

    Just to be anal retentive …

    Surely you mean “a decrease in activity in grey matter in brain regions”?

    (Thumbs up on “grey”, though.)

  8. #8 Sili
    November 27, 2007

    Bah! The Bierce/Hartman/McKean/Skitt Law of Prescriptive Retaliation strikes again.

    Sorry ’bout the bad tag.

  9. #9 sailor
    November 27, 2007

    “namely a decrease in grey matter in brain regions associated with the suppression of responses and habits.”
    Are we talking about the prefrontal cortex?

  10. #10 Marcus Ranum
    November 27, 2007

    Is this genetic link for all OCD? I’m not up on the science of OCD – forgive me if that’s a stupid question.

    I thought there were lots of different OCDs. Has anyone done a study to see if, say, hand-washing appears to be genetic but anorexia is not?

  11. #11 Thanny
    November 27, 2007

    It’s definitely more complicated than OCD or not OCD.

    My grandmother had a non-severe form of OCD with regards to many things. Not count-the-bricks OCD, mind you.

    Some of that has been inherited from her, no doubt. As an example, I noticed one day a while ago that I arrange currency in my wallet the same way as my father (her son). I didn’t learn it from him – it’s not something I saw him doing and copied. We unfold bent corners, orient bills in the same way (i.e. facing the same direction and portrait right side up). We also sort the bills by denomination first, and quality second (so the more raggy bills are spent first).

    Not long ago, I brought this up at my aunt’s house (his sister), during a small family get-together. My aunt and at least one of my cousins do very similar things with money, as does my uncle (who has distinctly more OCD than the rest of us).

    But my room is a mess, I abhor cleaning, and I can’t imagine being bored enough to count random objects in a room. I’m just a “perfectionist” about certain things.

    So OCD is definitely a mixed bag, and it’s definitely inherited, based on my own family experience.

  12. #12 nacky
    November 28, 2007

    A long time ago one of the villagers noticed that Gorg bowed to the rising sun every morning for as many times as he had fingers on his hands. He asked him why he did this. Gorg answered that he uh, just did it. The villager pressed him until Gorg said that he thought if he didn’t do it, something awful would happen. “What then?”, pressed the villager further. “The sun won’t rise!”, replied the obviously distressed Gorg. “And that bit where you walk around your hut several times in the evening?” “That’s to keep rocks from the sky from falling on the village:” Tapping the ground before eating?” “Keeps sickness away”.

    After a few months more devoid of eternal darkness, rocks from the sky and sickness, the villager decided Gorg must be doing something right and informed the other villagers. They almost all agreed that Gorg must be right and joined him in his rituals. Those not joining in were thrown out of the village as they were obviously not interested in village welfare. More rituals were found and vigorously enforced as well as forcefully imposed upon neighboring villages.

    Yeah, OCD starting a religion. Now pick the ending:
    1. Gorg sleeps late one day, the sun rises and:
    a. villagers rampage killing the new priests and returning to the old ways.
    b. villagers declare the sun fixed, Gorg a god, and become more fanatical
    2. Gorg loses a finger in a hunting accident and the world comes to an end when he can’t decide how many times to bow.

  13. #13 Kris Verburgh
    November 28, 2007

    “namely a decrease in grey matter in brain regions associated with the suppression of responses and habits”. Which brain regions? Because now I have read this article for nothing ;-)