March 21, 2006
Genetic Variant Predisposes To Cocaine Addiction

A variant of a neurotransmitter dopamine transporter gene increases risk of cocaine addiction by 50%.

Scientists have discovered that our genes have an impact on our reaction to cocaine and our likelihood of developing an addiction to the class A drug. The research is published this week in the online edition of PNAS, the journal of the American Academy of Sciences. It was carried out at the Medical Research Council (MRC) Social, Genetic and Developmental Research Centre at the Institute of Psychiatry, King’s College London.

Much of our desire to use/re-use drugs and the process of addiction depend on their impact on brain function. Cocaine’s action within the brain is relatively well understood. It strongly binds and inhibits the action of a protein called the Dopamine Transporter (DAT)1.

Addiction Potential

In this latest study, researchers examined the DNA of 700 cocaine abusers and 850 ordinary people and found that cocaine abusers had a specific genetic variation in DAT more frequently than the control subjects. People carrying two copies of this variant were 50% more likely to be cocaine dependent.

Expect a continuing stream of reports of genetic variants that heavily influence human behavior. Do humans have any free will at all? Heck if I know. But I'm not betting on it. My guess is my genes insist to me that I have no free will and I believe what they tell me.

Some day we'll all know our complete genetic profiles. We'll know for which drugs we have a greater risk of addiction. Will that knowledge reduce the incidence of drug addiction?

My guess: preventive treatments will play a bigger role in reducing drug addiction than genetic screening. Give Mom and Dad a vaccine or maybe a nanotech implant that'll eat up heroin, cocaine, ecstasy, and other drugs in the bloodstream and Junior won't get high until he can afford medical treatments that'll reverse the drug-neutralizing technologies that his parents had implanted in him when he was 12 years old.

Share |      Randall Parker, 2006 March 21 09:51 PM  Brain Addiction

Jake said at March 22, 2006 7:01 AM:

It also means that drug addiction could be cured or at least made more manageable with a DNA altering drug.

Lono said at March 22, 2006 8:06 AM:

Hmm... Guess I got the good variant - tried it in college and I couldn't stand the stuff!

Felt like a trip to the dentist - no thanks!

And I have an addictive personality...

(Thankfully Internet addiction has minimal social and physiocal side effects)

Dave said at March 22, 2006 9:40 AM:

Free will is an interesting question.

If you believe genes (natural instincts) have a powerful impact on human behaviour, as I do, it raises very interesting questions about what will happen when we transcend biology.
Will we then have truely free will, and will that be as big an improvement as it sounds?

Paul Dietz said at March 22, 2006 12:39 PM:

raises very interesting questions about what will happen when we transcend biology. Will we then have truely free will,

I suspect the stable state will be a coercive authority imposing changes in human nature on its subjects. You will love big brother; you'll be modified so you can't do otherwise.

So, the answer is 'no'.

Jake said at March 22, 2006 3:10 PM:

Separated twin studies have shown that genes account for 70% of your personality, interests and intelligence.
These studies have been done a number of times in different countries with over 100,000 separated twins tested. They all come up with the same result:

Genes account for 70% of your personality, interests and intelligence.

Antinomy said at March 22, 2006 7:10 PM:

Jake, I heard it was more like 50% for personality.

Jake said at March 23, 2006 5:56 AM:


I went to a Nobel Conference on Nature versus Nuture a few years ago.

If the speaker received his degree before 1970, he believed that genes accounted for only 30% of your personality. However, If the speaker received his degree after 1970 when the separated twin studies first came in, he believed that genes accounted for 70% of your personality.

It was a battle royal between both sides. It did not help that it pitted old researchers against young ones.

Randall Parker said at March 23, 2006 1:59 PM:


It is my recollection that Arthur Jensen and Phil Rushton now think IQ is 80% inherited in developed countries. I'm too busy at the moment to dig up a URL on that.

Personality is harder to measure and psychometricians I've asked say that personality tests are not as good at measuring personality as IQ tests are at measuring IQ. So calculations on what percentage of a personality characteristic is inherited are based on poorly measured attributes. So I take claims of 50% hereditability of personality characteristics with a grain of salt.

Anonymouse said at March 23, 2006 2:30 PM:

Well, imagine if we have the ability to change, at will, the way our brain operates? If we had like a switch that we could flip into one of any of hundreads of different modes... If we have that ability, can you say we have free will?

Bob Badour said at March 23, 2006 3:12 PM:

We can say we have free will without that switch so why wouldn't we be able to say it with one?

Randall Parker said at March 23, 2006 6:01 PM:

Whether we'd say we had free will with a complex switch in our brain would depend on which position the switch was in. Given the right position we'd vociferously claim and believe we did have free will. Given another position of the switch we'd take the opposite position.

Russ said at March 24, 2006 5:26 AM:

Physical addiction is usually the easiest thing to beat for any person who suffers from drug addiction. It is the mental/emotional need that the drug fills that is the real problem. For most people spirituality is the only thing that can adequately replace that need. I'm afraid no DNA sequencing or other pill is going to solve this funamentally human problem.

Anonymouse said at March 24, 2006 7:23 AM:

>> Whether we'd say we had free will with a complex switch in our brain would depend on which position the switch was in. Given the right position we'd vociferously claim and believe we did have free will. Given another position of the switch we'd take the opposite position.

I kind of doubt it'd be that clean-cut. For starters, beliefs aren't determined by simple binary switches; temperaments are. Let's say that someone has a temperament that makes them prone to sentimentality. Let's say that person was so sentimental that they jumped through mental hoops to convince themselves that free will existed. If you switch that off, all of the logic-pathways that had previously been set up to reconcile belief with that temperament wouldn't just disappear. If anything, it'd be a slow process (if it would change at all).

Even if you can change your temperament, there's still a lot of data and connections that are collected that won't just disappear.

No-pork said at March 24, 2006 7:27 AM:

can you please pretty please site that twin study that shows that your personality are 70% your genes?

without it is seems like a pretty clean shot at racism to me

but what do i know? my genes are inferious

T. J. Madison said at March 24, 2006 9:01 PM:

Randall, do you have any data comparing female identical twins to male identical twins? I would expect that male twins would be "more similar" in personality and IQ than female twins since the female twins will have a different X-chromosome inactivation pattern in brain tissue. In order to isolate the genetic component of IQ it would seem reasonable to only use male twins, especially since so many brain-related genes are on the X.

Completely Scientific and Unbiased Datapoint: My girly-girl's twin sister has quite a different personality, though her IQ is about the same (~145). "My" twin is much nicer and prettier, of course.

Randall Parker said at March 25, 2006 7:45 AM:


One can design electronic systems where the simple flip of a single switch causes a huge number of other switches to change positions. If it becomes possible to change the settings of enough neurons then flipping a single switch ought to be able to change not just moods (drugs can already do that) but specific beliefs as well.


I've passed your question along to some people who know. I'll post the results if I hear anything.


I predict that drugs and gene therapies that cure addictions will be developed within 10 years.

Anonymouse said at March 25, 2006 1:01 PM:

Considering how completely different everyone's brain is, and the fact that ones beliefs are collected over a lifetime rather than developed in the womb, I kind of doubt that all the circuits that control a belief in one person are going to be quite the same in another. Given that, it'd probably always be very complex to figure out how to do that in any individual, and there aren't really any worthwhile applications (unlike altering someone's mood) other than mind control.

the dopeman said at March 27, 2006 10:55 PM:

Drugs have been a really frustrating issue for me. I became addicted to the active ingredient in cough syrups--dextromethorphan(DXM). At first it was great--it lifted my constant attention deficit and depression, anxiety, and frustration. I could accept things that angered me. But now, it's just trouble. It provides a tantalizing escape from that which discomforts or annoys me, but gets me into more trouble than it's worth in the end. For some reason, I thought using a legal, over-the-counter medicine (if for off-the-label purposes, to put it euphemistically) was OK--or, in any case, not as bad as my other vices. Unfortunately, I have learned DXM and drugs in general(including alcohol) are far worse than vices I used to think of as having a greater "yuck" factor (e.g. sex, overeating, eating unhealthily) than a nice little molecule like the angelic DXM molecule.

In conclusion of this stream of conciousness,

David said at December 2, 2007 5:05 AM:

Its no surprise that genes make up a concrete part of person's propensity to fall into an addiction.

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