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Brains may be wired for addiction

By catseye, Feb 3, 2012 | Updated: Feb 11, 2012 | | |
  1. catseye
    Red areas show parts of the brain more active in drug users. Blue regions are abnormally decreased in drug users.

    Abnormalities in the brain may make some people more likely to become drug addicts, according to scientists at the University of Cambridge.

    They found the same differences in the brains of addicts and their non-addicted brothers and sisters.

    The study, published in the journal Science, suggested addiction is in part a "disorder of the brain".

    Other experts said the non-addicted siblings offered hope of new ways of teaching addicts "self-control".

    It has long been established that the brains of drug addicts have some differences to other people, but explaining that finding has been more difficult.

    Experts were unsure whether drugs changed the wiring of the brain or if drug addicts' brains were wired differently in the first place.

    This study, funded by the Medical Research Council, attempted to answer that by comparing the brains of 50 cocaine or crack addicts with the brain of their brother or sister, who had always been clean.

    Both the addicts and the non-addict siblings had the same abnormalities in the region of the brain which controls behaviour, the fronto-striatal systems.

    The suggestion is that these brains may be "hard-wired" for addiction in the first place.

    Lead researcher Dr Karen Ersche said: "It has long been known that not everyone who takes drugs becomes addicted."

    She told the BBC: "It shows that drug addiction is not a choice of lifestyle, it is a disorder of the brain and we need to recognise this."

    However, the non-addicted siblings had a very different life despite sharing the same susceptibility.

    "These brothers and sisters who don't have addiction problems, what they can tell us is how they overcome these problems, how they manage self-control in their daily life," Dr Karen Ersche said.

    Dr Paul Keedwell, a consultant psychiatrist at Cardiff University, said: "Addiction, like most psychiatric disorders, is the product of nature and nurture.

    "We need to follow up people over time to quantify the relative risk of nature versus nurture."

    It is possible that the similarities in the sibling's brains may not be down to genetics, but rather growing up in the same household. Research on the relationship between addiction and the structure of the brain is far from over.

    However, many specialists believe these findings open up new avenues for treatment.

    "If we could get a handle on what makes unaffected relatives of addicts so resilient we might be able to prevent a lot of addiction from taking hold," said Dr Keedwell.

    The chief pharmacist for Derbyshire Mental Health Trust, David Branford, said the study, "implies that addiction does not produce noticeable changes to brain structure and function which means that there may be provision for looking at new treatment techniques for addiction".

    Prof Les Iversen, from the department of pharmacology at the University of Oxford, said: "These new findings reinforce the view that the propensity to addiction is dependent on inherited differences in brain circuitry, and offer the possibility of new ways of treating high-risk individuals to develop better 'self control'."


    By David Shukman Science Editor, BBC News

    I met two of the participants in the study in Cambridge yesterday.

    Sophia has the pallour and nervousness of a long-term user of cocaine and crack. Her elder sister Teresa is smartly-dressed and describes herself as a control freak.

    They went through the tests and the scans and were surprised to find that they share the same abnormalities of the brain. It's a discovery that makes their contrasting lives all the more remarkable.

    Sophia is receiving treatment but admits she has trouble with self-control. Theresa, with a similar biological predisposition to addiction, has found the strength of character to stay clean.

    Poles apart, they are nevertheless devoted to each other and these findings bring them closer. A unique project has an unexpectedly moving outcome.

    By James Gallagher
    Health and science reporter, BBC News
    2 February 2012



    Abnormal brain structures hint at poor self-control and vulnerability to drug addiction

    [IMGL=white]http://www.drugs-forum.com/forum/attachment.php?attachmentid=24551&stc=1&d=1328283853[/IMGL]Our lives are full of instances where have to hold ourselves back. We stop ourselves from eating that tempting slice of cake to avoid putting on weight. We bite our tongues to avoid insulting our friends. We slam on the brakes to avoid killing a pedestrian. To quote Yoda: “Control! Control! You must learn control.”

    People with drug problems clearly have a problem with this. Their ability to resist their own impulses falters at the promise of the next hit. Now, scientists are starting to understand the changes in the brain that underlie these problems.

    Karen Ersche from the University of Cambridge found that drug users have abnormalities in parts of the brain that are important for inhibiting unwanted actions [*]. These same anomalies even exist in the brains of their siblings, who don’t have any drug problems themselves. They could act as a marker for people who are vulnerable to addiction. “Our findings provide further evidence for drug addiction being a brain-based disorder,” says Ersche.

    This is far from the first study to examine the brains of drug users. But it’s never been clear whether changes in such brains were caused by drugs, or made people vulnerable to addiction in the first place. Both are possible. Stimulant drugs typically act on parts of the brain involved in motivation, and interfere with those that inhibit our impulses. But these effects could be worse if these neural circuits are already weak.

    To separate these possibilities, Ersche studied 50 volunteers who had a long history of drug abuse. She compared them to their siblings, who had no drug problems, and to 50 unrelated volunteers who were also drugs-free. All of the recruits sat through a stop-signal test – a commonly used way of measuring self-control. Volunteers have to respond as quickly as possible to a stream of on-screen symbols – say, by pressing a key. If they hear a tone, which pops up unpredictably, they have to restrain themselves. (link edited out).

    The drug users struggled with the test compared to the unrelated volunteers, and needed more time to withhold their responses. Critically, their siblings fared just as badly, even though they weren’t using drugs. This strongly suggests that poor self-control isn’t the result of the drugs themselves, but of a shared (and probably inherited) vulnerability. “If you have brain with existing problems, the drugs have an easier play. It’s easier for them to take over,” says Ersche.

    Ersche found the same pattern when she looked at her volunteers’ brains. First, she focused on their white matter tracts – the fibres that transmit signals from one area to another. These are the brain’s communications network, and their density indicates how good different areas are at shuttling information between them.

    These connections were weaker among both the drug users and their relatives, compared to the healthy unrelated volunteers. The fibres were particularly sparse around the right inferior frontal cortex (IFC), an area involved in controlling our inhibitions. These abnormalities were linked to the volunteers’s scores on the stop-signal test – the weaker the connections, the slower their reaction times. With its communication lines weakened, the IFC was less able to exert its suppressive influence.

    The siblings also shared anomalies in the size of some brain areas. Their putamens and medial temporal lobes were bigger, and their posterior insulas were smaller. All of these areas have been implicated in learning and memory. “This may be an indicator of an enhanced propensity to form habits,” says Ersche.

    From these results, a cohesive picture emerges. Some parts of the brain are larger, increasing the attractiveness of potential rewards, and the odds of habitual, addictive behaviour. The IFC, which would normally suppress such desires, has less of a say because the fibres connecting it to other parts of the brain are weaker. It’s like having a mob of reckless friends who are egging each other on over fast broadband connections, while their sensible parents send them words of caution on a dial-up modem.

    This is uncannily similar to what happens in the teenage brain, where areas associated with reward mature before the prefrontal areas that exercise restraint. Other scientists have suggested that this gap in timing explains why teens are so prone to risky and impulsive behaviours. They’re not making thoughtless decisions – they simply weigh risks and rewards in a different way to adults. Perhaps people who are vulnerable to addiction never grow out of this asymmetry between desire and inhibition. “It does look like a developmental problem,” says Ersche, “but we really need to compare these brains to those of adolescents to know for sure.”

    “This is a very important and well-designed study,” says Susan Tapert from the University of California, San Diego. She adds, “It will be important to understand how the non-drug dependent volunteers were able to avoid drug problems given same brain features as their siblings.”

    This is a key point. Drug dependence runs in families, and it is clearly influenced by a person’s genes. But genes do not determine behaviour; they merely influence it. The non-addicted siblings in Ersche’s study illustrate the point beautifully. “They share so much,” says Ersche. “They have the same vulnerabilities as their drug-dependent brothers and sisters. They had a lot of domestic violence and troubled childhoods but they didn’t get into drugs. Their average age was 33. They may have had many opportunities to develop dependence, but they didn’t.”

    Perhaps the other one had environmental influences that set them down a different path. Perhaps they also had inherited some “resilience factors” that their siblings did not. In an earlier study with some of the same siblings, Ersche found that all of them are more impulsive, but only the drug users were “sensation-seekers” [**]. These are subtly different traits. “Impulsive people act on the spur of the moment,” Ersche explains, “but sensation-seekers crave excitement and adventure. In contrast to the drug-dependent individuals, their siblings do not seem to crave for excitement and sensations, which might have protected them from taking drugs in the first place.

    In the meantime, Ersche’s study suggests that the white fibre tracts around the IFC could be used as a marker for vulnerability to addiction. That’s useful for two reasons. We could use it to identify people who are most at risk of abusing drugs, before they actually encounter any problems. We could also see if people can strengthen the connections in this critical area. Many scientists have developed programmes for improving self-control at an early age. Monitoring the IFC’s white matter could provide an objective way of measuring whether those programmes are working. As Tapert says, “We might be able to modify these risky brain characteristics, to see if the misuse of drugs can be reduced.”

    Reference: Ersche, Jones, Williams, Turton, Robbins & Bullmore. 2011. Abnormal Brain Structure Implicated in Stimulant Drug Addiction. Science

    February 2nd, 2012 by Ed Yong



    Science 3 February 2012:
    Vol. 335 no. 6068 pp. 601-604
    DOI: 10.1126/science.1214463

    [*] Abnormal Brain Structure Implicated in Stimulant Drug Addiction

    Karen D. Ersche1,*, P. Simon Jones1, Guy B. Williams1,2, Abigail J Turton1, Trevor W. Robbins1, Edward T. Bullmore1,3,4

    Addiction to drugs is a major contemporary public health issue, characterized by maladaptive behavior to obtain and consume an increasing amount of drugs at the expense of the individual’s health and social and personal life. We discovered abnormalities in fronto-striatal brain systems implicated in self-control in both stimulant-dependent individuals and their biological siblings who have no history of chronic drug abuse; these findings support the idea of an underlying neurocognitive endophenotype for stimulant drug addiction.

    Source: International weekly science journal (Sciencemag)


    Biol Psychiatry. 2010 Oct 15;68(8):770-3. Epub 2010 Aug 1.

    [**] Drug addiction endophenotypes: impulsive versus sensation-seeking personality traits.

    Ersche KD, Turton AJ, Pradhan S, Bullmore ET, Robbins TW.
    Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom. (e-mail edited out)


    BACKGROUND: Genetic factors have been implicated in the development of substance abuse disorders, but the role of pre-existing vulnerability in addiction is still poorly understood. Personality traits of impulsivity and sensation-seeking are highly prevalent in chronic drug users and have been linked with an increased risk for substance abuse. However, it has not been clear whether these personality traits are a cause or an effect of stimulant drug dependence.

    METHOD: We compared self-reported levels of impulsivity and sensation-seeking between 30 sibling pairs of stimulant-dependent individuals and their biological brothers/sisters who did not have a significant drug-taking history and 30 unrelated, nondrug-taking control volunteers.

    RESULTS: Siblings of chronic stimulant users reported significantly higher levels of trait-impulsivity than control volunteers but did not differ from control volunteers with regard to sensation-seeking traits. Stimulant-dependent individuals reported significantly higher levels of impulsivity and sensation-seeking compared with both their siblings and control volunteers.

    CONCLUSIONS: These data indicate that impulsivity is a behavioral endophenotype mediating risk for stimulant dependence that may be exacerbated by chronic drug exposure, whereas abnormal sensation-seeking is more likely to be an effect of stimulant drug abuse.

    Copyright © 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
    PMID: 20678754 [PubMed - indexed for MEDLINE]

    Source: NCBI, National Center for Biotechnology Information
  2. somnitek
    I'm starting to wonder, if addiction is maybe an undiscovered (as, but...) relatively natural part of some individual development, triggered by specific drug use, maybe. Still, rather than avoid addiction, maybe if a parent knowingly possessess the trait, and foresees a potential issue, consider: If the problem can't be avoided in one's children, and assuming the parent is either living stable, and or recovered, I would see that more as an opportunity to guide a younger addict through the toughest parts of re-stabilizing one's life, perhaps in preparation for more long-term recovery, while also helping to avoid some of the more serious common perils of having a habit. It's almost already a rite of passage in some families I know. It's just almost unavoidable for the children of these addicts to avoid at least a little dabbling, with some who tend to stumble on to a specific, re-occuring, problem drug developing addiction. Rather then face abandonment. The family can relate and binds together for the long or short term haul, either or. It seems a lot more common than even a generation ago.
  3. venkecske
    You may want to visit Dr. Karen Ersche's site at Cambridge Neuroscience(UK) and the uploaded manuscript there (under Publications) And do not forget to read the Introduction there by Andrew Huxley; Sir Andrew is half-brother of Aldous Huxley.
  4. catseye
    ^^ superb job, venkecske :)
    I have uploaded the article to the archives and it can be found HERE
  5. war209
    I thought in genes of some people or people that lack dopamine that when they get dopamine it is really intensive.

    Like some one that drinks alcohol ,look at porn ,masterbate or have sex it feels good and you want to do it again !! But for people that have these genes or lack dopamine it feels so much more intensive when you drink alcohol ,look at porn ,masterbate or have sex than other people.
  6. catseye
    Sure, drug use can and does impact the brain - there is also an interesting theory that brain injury actually pre-dates addiction in some people...see the news story HERE.
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