h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I have just heard that my cousin has taken an accidental overdose and there are others in my family who seem to struggle with substance abuse and I wondered if there was a genetic element to addiction, if some people are more susceptible to certain types of drugs? Or to addiction generally?

Accidental overdose of what though.

It is possible to take an accidental overdose of prescribed drugs or over-the-counter medicines by failing to follow instructions or forgetting when the last dose was taken and taking another one.

If you are talking illegal drugs then I'm not so sure that an overdose can be truly classified as accidental because there was a deliberate choice to take the substance in the first place. (Sorry I'm being a bit moralistic there).

There is a genetic component to addiction but I suspect that social influences carry more weight.

t.

Illegal substances in some kind of cocktail. I think they use the term accidental to distinguish it from attempted suicide. The cousin has had some troubles with drugs before and was supposed to be clean now, doing AA and all that.

I believe that a mother who takes certain drugs will pass parts of those substances to the baby through the umbilical cord and make them more susceptible to those drugs later in life. And I do believe there is a genetic component besides that.

http://www.livestrong.com/article/18004-effects-substance-abuse-unborn-babies/

Found out toxins are passed through the umbilical cord, I have not found anything about the same addiction being easier to get, although it can cause lower mental abilities which would create more social pressure to do drugs.

Difficult question what are you defining as a genetic element?

Do you mean personality-wise? I.e. a genetic element to having and addictive personality?

If so, how do you filter out nurture a peer pressure away from genetic traits?

If you mean a physical/biochemical mechanism then that is to my knowledge beyond our current abilities to know.


My gut feeling would be - almost certainly. But how you definitively prove it, I've no idea.

The former point maybe known of course -but it's away from my level of expertise so I can't really comment beyond what I've already said.

Of course there is the brutally obvious thoughtline that goes like this.


We can get addicted to nicotine.

Presumably banana trees cannot.

Hence there must be a genetic element to it as we are genetically different to bananas.

(But I suspect you wanted something rather deeper than that )

I like it

Most, if not all, drugs we can get addicted to work by binding to cell surface receptors, so, logically I'd guess like with anything of that type, there will be genetic variability in expression in the number of these receptors in certain individuals, and, I'd guess therefore some people might lack them all together... There's also an increase in the amount of these receptors, following frequent exposure to some drugs, which I'd imagine helps fuel the addiction, and sense of more of the drug, or more stronger and differnt drugs also being needed, there must be a genetic componant to the level at which an invidual can or can't upregulate expression of teh genes necessary to express more cell surface receptors....

Asides which, the familial clustering particularly of things like alcoholism must provide some evidence for a genetic basis, though of course I'd imagine the social aspect, of exposure to alcohol might have an influence, it could just as easily have a counter affect, of turning individuals away from the addiction, so that is hard to quantify Iguess...

I might have answered my own question. I've just been reading about a study done in twins. Apperently with identical twins if one has an addiction it is more likely that the other will than it is in non-identical twins which I think suggests the gentic connection I meant. Taking social factors out it suggests that there is a link. I hadn't even been aware of the clustering of alcholism. I'm quite interested in this now.

Although I don't have any details on the study so it could be flawed.

I've found the details of the study (in the unluikely event that anyone else is interested). I thought it was an interesting read.

Prescott CA, Kendler KS. Genetic and environmental contributions to alcohol abuse and dependence in a population-based sample of male twins. American Journal Psychiatry. 1999 Jan;156(1):34-40.

The article is here:

http://ajp.psychiatryonline.org/data/Journals/AJP/3696/34.pdf

Twins are a massive social/peer pressure on each other though surely.
*very* hard to factor it out there (impossible really unless the twins are separated from birth - there might be rare cases of that it's seen occasionally in other studies)

It is indeed true that alcohol clusters - and it's also certainly true that it puts as many off alcohol as it does encourage others.
I think that's more or less purely social as far as I'm aware. Basically the line goes that people in an alcoholics household don't get exposed to responsible/moderate drinking so they aren't really aware of what that is so they're far more likely to go either way in terms of drinking - all or nothing...

This compared identical twins to non-identical twins. Identical twins will have more common genetic material than non-identical. It is assumed that the two groups would have equal amounts of common upbringing/schooling etc.

yes, I didn't read your link until after I posted. My bad.

I'm just doing a quick rummage on pub med, and I have found some interesting stuff.

1. It's complex : http://www.bsos.umd.edu/psyc/addiction/Psyc434/Tsuang%202001.pdf there's a huge variety of environmental and behavioural factors, but there's a thought from twin studies that genetics may play a role.

2. It may be to do with dopamine.

Dopamine is neurotransmitter, and it's release is associated with feelings of pleasure, so it's thought that when you do something which results in a pleasurable sensation (such as eat food, have sex..) then dopamine is released. It looks like variations in the dopamine receptors are possibly related to the genetics of addiction.

http://www.ncbi.nlm.nih.gov/pubmed/19179847

Comparing identical/non-indentical twins is a good way to look at genetic studies by the way...

That is interesting. Although I did find myself laughing at the 'scientists discover people who experience pleasurable sensations when smoking marijuana are more likely to try it again'.

It was interesting to see that heroin seemed to react differently to the other drugs- made me realise what a stereotyped idea I had of heroin use as I found myself wondering if users were less likely to get the opportunity to pass on their genes.

It was interesting that there seems to be a genetic link to how easy you find it to give up smoking. Some people I know seem to have found it very easy to give up and can't understand whilst others don't.

And zygosity is a great word.

>scientists discover people who experience pleasurable sensations when smoking marijuana are more likely to try it again'<

Well that'll be journos showing their ignorance rather than the scientists to be fair.
It is a rare day indeed that scientific findings get reported accurately in the popular press.

It is something that is said in the paper but it wasn't the point. It's just that it flashed in front of my eyes as a newspaper headline.

I mean it wasn't the point the paper was making, it was building up an argument.