1. Drinking during adolescence can alter brain cell nerve growth

    June 24, 2017 by Ashley

    From the Research Society on Alcoholism press release:

    The developmental period from adolescence to adulthood is accompanied by a greater vulnerability to addictions — including alcohol use disorders — than is seen in other periods of life. This increased risk may be due to genetic predisposition, poor impulse control, or heightened sensitivity of the still-developing brain to drug-related toxicity. This report describes a study in mice of the neurobehavioral impact of chronic, intermittent alcohol-vapor exposure during adolescence, in an effort to model periodic heavy drinking and compare it with similar drinking behavior during adulthood.

    Researchers conducted two parallel tests in adult male mice following their exposure to alcohol vapors during adolescence (4-6 weeks old) or adulthood (8-10 weeks old). First, they tested the adult mice for changes in the density and structure of dendritic spines (nerve endings) in the infralimbic cortex (IL), prelimbic cortex (PL) and basolateral amygdala (BLA) regions of the brain. Second, they tested the adult mice for alcohol drinking, sensitivity to alcohol intoxication, blood-alcohol clearance, and measures of response to food reward.

    Chronic exposure to alcohol vapors during adolescence produced significant, persistent, and strong regional-specific alterations in neuronal dendritic spine density in IL and BLA neurons, accompanied by a limited set of behavioral alterations. Comparable effects were not seen in the mice exposed to alcohol only during adulthood. Together, these data demonstrate that specific key brain circuits are vulnerable to alcohol’s effects during adolescence, with lasting and potentially detrimental consequences for behavior.


  2. Anticipation helps pathological gamblers hold out for larger-but-later rewards

    June 19, 2017 by Ashley

    From the Society for Neuroscience press release:

    Triggering pathological gamblers to envision a future personal experience reduces their preference for an immediate reward over a larger, delayed award, according to a study published in eNeuro.

    Pathological gambling is a behavioral addiction associated with preference for a smaller but more immediate reward over a larger reward in the future. In the brain, the nucleus accumbens (NAcc) and ventromedial prefrontal cortex (vmPFC) are thought to encode how these rewards are valued.

    Antonius Wiehler and colleagues presented 24 male pathological gamblers and 24 healthy men with a choice between an immediate monetary reward or a larger-but-delayed reward, while also reminding them of a future personal event such as an upcoming vacation. The researchers found that thinking about this future event might shift reward preference and its associated representation in the brain in the pathological gamblers. Brain activity while thinking about the future event was similar in both the pathological gamblers and healthy men. A correlation between decision-making and activity in the hippocampus was found only in healthy men, suggesting a possible role for this region in regulating impulsive behavior. These findings suggest interventions that enhance the value of future rewards may be effective in reducing impulsive decision-making in pathological gamblers.


  3. Study links sleep disturbances to higher incidence of substance use among college athletes

    June 16, 2017 by Ashley

    From the American Academy of Sleep Medicine press release:

    Preliminary results of a new study show that sleep disturbance is strongly related to the use of alcohol, tobacco, and illicit drugs among student athletes in college.

    Results show that student athletes with sleep difficulties were 151 percent more likely to use cigarettes, 36 percent more likely to drink alcohol, and 66 percent more likely to smoke marijuana. Sleep difficulties also predict an increased use of controlled, illegal, and banned substances. For example, student athletes with sleep difficulties were 317 percent more likely to use methamphetamine, 349 percent more likely to use cocaine, and 175 percent more likely to use steroids.

    “The most surprising thing was the consistency with which sleep difficulties among student athletes predict increased use of many substances, including substances that are illegal and banned,” said senior author Michael Grander, PhD, director of the Sleep and Health Research Program at the University of Arizona in Tucson. “Across the board, students with sleep difficulties were more likely to smoke, drink, and use illegal substances.”

    The study involved an analysis of survey data completed from 2011 to 2014 by 8,683 student athletes at U.S. colleges and universities as part of the National College Health Assessment conducted by the American College Health Association. Participants were asked whether, in the past 12 months, “sleep difficulties” had “been traumatic or very difficult for you to handle.” Students also were asked whether they had used a list of specific substances in the past 30 days.

    Regression analyses examined whether use of any of these substances was associated with sleep difficulties, adjusted for age, sex, and survey year. Also, discrepancy between student use and perceived typical use and sleep was examined.

    “Sleep difficulties are quite common among students and especially student athletes,” said lead author Chloe Warlick, research assistant in the Sleep and Health Research Program. “Substance use is also a major public health problem. These results not only underscore the important link between sleep difficulties and substance use, but they show that this relationship is quite strong, even among student athletes.”

    Grandner added that the findings have important implications for both student health and athletic performance.

    “Knowing this association between sleeping difficulty and substance abuse could be beneficial for coaches, physical therapists, and physicians,” he said. “These findings could provide important insight when treating sleep disturbances or attempting to improve athletic performance.”

    The authors concluded that sleep-focused interventions should be evaluated to determine whether they decrease use of psychoactive substances.


  4. Study suggests oxytocin reduces cravings for methamphetamine

    June 15, 2017 by Ashley

    From the Elsevier press release:

    Many people have suggested that addiction hijacks the body’s natural drives in the service of compulsive drug use. A new study now suggests that hijacking another natural system in the brain may help overcome drug addiction. Published in Biological Psychiatry, the study shows that administration of oxytocin — a naturally occurring molecule well known for its role in social bonding and childbirth — reduces drug-seeking behavior in methamphetamine-addicted rats.

    “There are virtually no pharmacotherapeutics for methamphetamine addiction, a chronically relapsing disease that destroys many lives,” said first author Dr. Brittney Cox, now at the University of California Irvine. “Our results are important because they support development of novel, oxytocin-based therapeutics for methamphetamine abuse in humans.”

    To show this, Cox and colleagues developed a new method to assess addiction-like behaviors with meth, which could not be studied with previous techniques because of the drug’s long-acting effects. The researchers allowed rats to self-administer meth using a paradigm designed to examine individual differences in the rats’ drug-taking behavior, then tested the effects of oxytocin on their motivation to acquire the drug.

    Although oxytocin administered to rats had no effect on the amount of methamphetamine they wanted when it required minimal effort, it strongly decreased the amount of effort rats were willing to exert to obtain the drug they desired, and it decreased relapse to methamphetamine seeking in both males and females.

    “Intriguingly, these effects were strongest in animals with the greatest motivation to seek methamphetamine, indicating that oxytocin has potential as a treatment for addiction,” said Cox.

    The study also pinpoints the brain region where the oxytocin has its effect. When Cox and colleagues infused oxytocin specifically into the nucleus accumbens, a small brain region implicated in drug addiction, they found that it had the same effects as when they administered it systemically. Infusion of an oxytocin blocker to the brain region blocked the systemic effects of oxytocin, driving home the necessary role of the nucleus accumbens for oxytocin’s effects.

    “It will be interesting to learn whether oxytocin has a direct effect on the rewarding effects of methamphetamine or whether these effects are modulated by this hormone’s effects on natural rewards, particularly social activity,” said Dr. John Krystal, Editor of Biological Psychiatry, referring to the mechanism behind the effects that remains to be determined.

    The researchers also found that using their new method, measures of motivation accurately predicted relapse behavior, which was not predicted by drug-taking itself when low effort was required. The technique used to assess addiction-like behavior in rats can also be used in humans, so if similar results are found in addicted people, the researchers hope the technique may help identify people most susceptible to addiction and be useful for predicting the efficacy of oxytocin treatment.


  5. Study suggests growing up in affluent communities may up risk for addictions

    June 13, 2017 by Ashley

    From the Arizona State University press release:

    They have what most would want — affluent upwardly mobile parents, living in comfortable homes in the suburbs, going to an elite high school and being groomed for the nation’s best colleges. And they appear to thrive in this setting — popular among their peers, performing exceedingly well in school, highly regarded by peers and teachers, and accomplished at a various extracurricular activities.

    But these “privileged” American high schoolers can be at high risk for problematic substance abuse across early adulthood, according to new research from Arizona State University.

    “We found alarmingly high rates of substance abuse among young adults who we initially studied as teenagers,” said Suniya Luthar, a Foundation professor of psychology at Arizona State University and a professor emerita at Columbia University’s Teachers College, who led the research. “Results showed that among both men and women and across annual assessments, these young adults had substantial elevations, relative to national norms, in frequency of several indicators — drinking to intoxication and of using marijuana, stimulants such as Adderall, cocaine, and club drugs such as ecstasy.”

    The paper, “Adolescents from upper middle class communities: Substance misuse and addiction across early adulthood,” appears in the current issue of Development and Psychopathology. It is co-authored by Phillip Small, an ASU graduate student in clinical psychology, and Lucia Ciciolla an assistant professor at Oklahoma State University.

    In the article, the authors describe a study of two groups of students in affluent communities in the Northeast U.S. as part of the New England Study of Suburban Youth (NESSY). The researchers assessed these youngsters as high school seniors and then annually across four college years (NESSY-Y, for the younger cohort), and across ages 23 to 27 (NESSY-O, for the older cohort).

    “We found rates of addiction to drugs or alcohol among 19 to 24 percent of women in the older cohort by the age of 26, and 23 to 40 percent among men. These rates were 3 and 2 times as high respectively, as compared to national norms,” Luthar said. “Among the younger cohort by the age of 22 years, rates of addiction were between 11 and 16 percent among women (close to national norms) but 19 to 27 percent among men, or about twice as high as national norms.”

    Luthar said a look into the lives of these adolescents provide some clues to the cause of these high rates of addictions.

    When the NESSY groups were first assessed, they all attended the best schools in the region — suburban schools with very high-standardized test scores, rich extra curricular offerings and high proportions of their graduates heading off to very selective universities. In general, kids at such schools experience enormous pressures to achieve, and many come to live by the dual credos of “I can, therefore I must” and “we work hard and we play hard” with the playing involving parties with drugs and alcohol.

    Also implicated is affluence in the school community.

    “Not all of these students were from wealthy families but most were; as parents typically had advanced educational degrees and median incomes much higher than national norms,” Luthar said. “And without question, most of the parents wanted their kids to head off to the best universities, as did the kids themselves.”

    With affluence comes ease in acquiring drugs, she added. “Many kids in these communities have plenty of disposable income with which they can get high-quality fake ID’s, as well as alcohol and both prescription and recreational drugs.”

    Other factors that exacerbate the risks, Luthar said, include widespread peer approval for substance use, and the fact that parents can be lulled into a false sense of security, believing that as their kids continue to perform well in school there could not be any serious underlying issues. As a result, they can become somewhat laissez-faire about detected alcohol or marijuana use.

    So what can be done to reverse this trend?

    “This is a problem that derives from multiple levels of influence, so we’re going to need interventions at multiple levels to tackle it,” Luthar said.

    “At the level of the kids themselves and their parents, it will be important to disseminate research findings — based on rigorous scientific data — that messing with drugs and alcohol really should not be trivialized as just something all kids do,” Luthar said. “The earlier children start to use and the more frequently they do, the more likely it is that they will develop addictions down the line.”

    Luthar pointed to strategies like sex education programs conveying the “bottom line” of risks involved, such as “it only takes once” to contract a sexually transmitted disease.

    “For high-achieving and ambitious youngsters, it could actually be persuasive to share scientific data showing that in their own communities the statistical odds of developing serious problems of addiction are two to three times higher than norms. And that it truly just takes one event of being arrested with cocaine, or hurting someone in a drunken car accident, to derail the high profile positions of leadership and influence toward which they are working so hard for the future.”

    On a second level is reducing the enormous pressure these kids are under trying to get into only the most selective universities.

    “As long as university admissions processes continue to be as they are — increasingly smaller number of admits per applications and requiring impossible resumes — these young people will continue to be frenetic in pursuing those coveted spots — and many will continue to self-medicate as a result,” explained Luthar. “An alternative approach, suggested by my colleague Barry Schwartz, could be to have these highly selective universities institute a lottery system for final admittance, given all other qualifications and resumes being equal.

    A second important measure would be showing the kids there are role models of adults who did not go to an elite university, but who picked a college because it felt right for them and who were highly successful in life.

    “It shows that there is, in fact, life, wisdom, financial solvency, creativity, and yes, happiness, beyond the walls of the Ivy Leagues,” Luthar said.

    A third factor is for leaders in science, public health and social policy to take seriously the fact that youth at high-achieving schools could be a population that is at inordinately high risk for addiction. Decades ago, developmental researchers established that children growing up in chronic poverty were at high risk for maladjustment, and this led, laudably, to a plethora of studies trying to figure out how best to minimize risks, and foster resilience among these youth by addressing different aspects of their environments.

    “We now need the same dedicated research on kids who grow up in pressure- cooker, high achieving schools,” Luthar said. “Paradoxical though it may seem, these ostensibly privileged youth, many of who start experimenting early and often with drinking and drugs, could well be among the groups at highest risk for alcoholism and addiction in adulthood.”


  6. Study finds internet withdrawal increases heart rate and blood pressure

    June 12, 2017 by Ashley

    From the Swansea University press release:

    Scientists and clinicians from Swansea and Milan have found that some people who use the internet a lot experience significant physiological changes such as increased heart rate and blood pressure when they finish using the internet.

    The study involved 144 participants, aged 18 to 33 years, having their heart rate and blood pressure measured before and after a brief internet session. Their anxiety and self-reported internet-addiction were also assessed. The results showed increases in physiological arousal on terminating the internet session for those with problematically-high internet usage. These increases in heart rate and blood pressure were mirrored by increased feelings of anxiety. However, there were no such changes for participants who reported no internet-usage problems.

    The study, published in the international peer-reviewed journal, PLOS ONE, is the first controlled-experimental demonstration of physiological changes as a result of internet exposure.

    The study lead, Professor Phil Reed, of Swansea University, said: “We have known for some time that people who are over-dependent on digital devices report feelings of anxiety when they are stopped from using them, but now we can see that these psychological effects are accompanied by actual physiological changes.”

    There was an average 3-4% increase in heart rate and blood pressure, and in some cases double that figure, immediately on termination of internet use, compared to before using it, for those with digital-behaviour problems. Although this increase is not enough to be life-threatening, such changes can be associated with feelings of anxiety, and with alterations to the hormonal system that can reduce immune responses. The study also suggested that these physiological changes and accompanying increases in anxiety indicate a state like withdrawal seen for many ‘sedative’ drugs, such as alcohol, cannabis, and heroin, and this state may be responsible for some people’s need to re-engage with their digital devices to reduce these unpleasant feelings.

    Dr. Lisa Osborne, a clinical researcher and co-author of the study, said: “A problem with experiencing physiological changes like increased heart rate is that they can be misinterpreted as something more physically threatening, especially by those with high levels of anxiety, which can lead to more anxiety, and more need to reduce it.”

    The authors go on to speculate that internet use is driven by more than just the short-term excitement or joy of the technology, but that over-use can produce negative physiological and psychological changes that may drive people back onto the internet, even when they do not want to engage.

    Professor Reed said: “The individuals in our study used the internet in a fairly typical way, so we are confident that many people who over-use the internet could be affected in the same way. However, there are groups who use the internet in other ways, like gamers, perhaps to generate arousal, and the effects of stopping use on their physiology could be different — this is yet to be established.”

    Professor Roberto Truzoli of Milan University, a co-author of the study, added: “Whether problematic internet use turns out to be an addiction — involving physiological and psychological withdrawal effects — or whether compulsions are involved that do not necessitate such withdrawal effects — is yet to be seen, but these results seem to show that, for some people, it is likely to be an addiction.”

    The study also found that the participants spent an average of 5 hours a day on the internet, with 20% spending over 6 hours a day using the internet. Additionally, over 40% of the sample reported some level of internet-related problem — acknowledging that they spend too much time online. There was no difference between men and women in the tendency to show internet addiction. By far the most common reasons for engaging with digital devices were digital communication media (‘social media’) and shopping.

    Previous studies by this group, and many others, have shown short-term increases in self-reported anxiety when digitally-dependent people have their digital devices removed, and longer-term increases in their depression and loneliness, as well as changes to actual brain structures and capability to fight infections in some.

    Professor Phil Reed said: “The growth of digital communication media is fuelling the rise of ‘internet’ use, especially for women. There is now a large amount of evidence documenting the negative effects of overuse on people’s psychology, neurology, and now, in this study, on their physiology. Given this, we have to see a more responsible attitude to the marketing of these products by firms — like we have seen for alcohol and gambling.”


  7. New study may pave way for treating alcohol addiction by reducing motivation to drink

    June 11, 2017 by Ashley

    From the Elsevier press release:

    A new study in Biological Psychiatry may pave the way for treating alcohol addiction by reducing motivation to drink, rather than by altering the effects of alcohol itself. Led by Drs. Kasia Radwanska and Leszek Kaczmarek of the Nencki Institute, Warsaw, Poland, the study reports a new mechanism behind alcohol seeking behavior.

    When people think about drugs to treat alcoholism, their first thought is usually a drug that stimulates or blocks a receptor for a chemical messenger. However, the new study highlights a process that changes brain activity by altering the network of proteins that surrounds nerve cells. This network of proteins, called the extracellular matrix, provides active support for the development and activity of nerve cells. The functions of the matrix are regulated, in part, by enzymes that break down matrix proteins; one of these enzymes is matrix metalloproteinase-9 (MMP-9).

    In the study, while mice had free access to alcohol to establish addiction-like behavior, those missing the enzyme MMP-9 (MMP-9 KO) drank just as much as normal mice. However, first author Dr. Marzena Stefaniuk and colleagues found that MMP-9 KO mice were less motivated to obtain alcohol when its access was restricted, and less persistent to seek alcohol during withdrawal — behaviors normally characteristic of addiction. The researchers were able to restore the impaired motivation by replacing MMP-9 in the central amygdala, a part of the brain’s emotional center that has also been implicated in alcohol dependence.

    “Interestingly, in human alcoholics, the MMP-9 gene polymorphism that leads to a higher MMP-9 production correlates with greater motivation to drink alcohol,” said Dr. Kaczmarek, referring to their analysis of 167 alcohol-addicted males compared with 199 control males, also included in the new study. Using a clinical assessment of alcoholism behavior, the researchers found that addicted people with a T allele in the MMP-9 gene continued to drink alcohol despite the negative consequences more frequently than patients with a C allele. The findings further support the role of MMP-9 in motivation for alcohol.

    “Matrix metalloproteinases play critical roles in brain function and disease that have only recently received intensive study,” said Dr. John Krystal, Editor of Biological Psychiatry. “The exciting study by Stefaniuk and colleagues implicates them in alcohol use disorders, but they are likely to play roles quite broadly in psychiatric disorders. It will be important to determine whether these proteins may be targeted therapeutically.”

    In previous studies, MMP-9 has been demonstrated to be mandatory in the central amygdala for formation of appetitive memory traces via synaptic plasticity — the structural and physiological alteration of synapses, the connections that facilitate communication between neurons. Indeed, the loss of MMP-9 in mice impaired structural and physiological alcohol-related alterations in the central amygdala, leading the authors to suggest MMP-9-dependent synaptic plasticity in this brain region as a new mechanism behind alcohol craving.

    “In aggregate, these findings point to MMP-9 as a novel therapeutic target in fighting alcohol addiction,” said Kaczmarek.


  8. Study looks at how signs of problem gambling differ in men and women

    June 10, 2017 by Ashley

    From the Springer press release:

    Men and women experiencing problems with gaming machines (slot machines) display the same signs that their habit is out of control. However, the two sexes differ in how they handle the distress that accompanies their addiction. Women tend to be more emotional and more likely to cry or to look depressed when losing. Men may angrily channel their distress into striking or even kicking their gaming machine. These are the findings of researchers at the University of Adelaide, the Australian Gambling Research Centre (AGRC) and Swinburne University of Technology in Australia. The study is published in Springer’s Journal of Gambling Studies.

    The data used in the paper were obtained from two recent large studies conducted in Australia of regular gamblers. Together the two surveys yielded a total sample of 1185 (580 men and 605 women). Of these, 338 were classified as problem gamblers.

    Men and women were found to show the same problem gambling symptoms, but some “red flags” of distress were more prevalent among the sexes. Males were more likely than females to report anger and frustration when losing. They more readily displayed aggression in their play, kicking and striking their gaming machines or playing them roughly. They often engaged in territorial stand-over tactics to scare customers away from machines that they claimed as theirs, and could be impolite towards venue staff. Women were much more likely to display visible signs of distress such as crying, or other visible signs of sadness and depression.

    “Signs of distress are likely to be more commonly seen indicators for female patrons while signs of anger or aggression may be more likely to be observed for males,” says Anna Thomas, Manager of the AGRC.

    Thomas advises gambling venue staff to view any unusual behaviours such as aggression towards machines, attempts to borrow money or ask for credit, or a decline in grooming in female patrons as definite “red flags”.

    “Behaviours that are most clearly distinctive of gambling problems in male patrons included clear and visible signs of distress, asking for loans from a venue and attempts to conceal their presence in venues from family and friends. For female patrons, asking a venue for a loan or a noticeable decline in personal grooming are particular indicators of which staff should take note,” Thomas adds.

    The results more broadly show that the behaviour of female problem gamblers is generally more differentiated from other lower risk gamblers. “This suggests that it may be easier to detect variations in behaviour for female gamblers than for males,” says Thomas. “It also means that staff may need to spend more time watching potential male problem gamblers before they can be confident that they are displaying behaviour that is different from other male gamblers.”

    The researchers advise that staff be trained to better identify behavioural indicators, to interpret these as a whole within the greater context, and on how to confidently use such information in their interaction with patrons. Some of this training might include a focus on gender differences and diversity in gamblers.


  9. Resetting balance in reward centers may help treat alcohol addiction

    June 9, 2017 by Ashley

    From the Elsevier press release:

    The human brain functions on a delicate balance of reinforcing positive behaviors and suppressing negative ones, which takes place in the dorsal striatum, a brain region critical for goal-directed behavior and implicated in drug and alcohol addiction.

    According to a new study in Biological Psychiatry, two pathways in the dorsal striatum that regulate this process — the “Go” pathway, which hits the gas for rewarding behaviors, and the “No-Go” pathway, which hits the brakes — have opposite effects to control alcohol drinking behavior. Led by Dr. Jun Wang of Texas A&M Health Science Center, the study reports that alcohol-induced alterations in the signaling of these two pathways reinforce alcohol consumption, possibly leading to alcohol abuse or addiction.

    Co-first authors Dr. Yifeng Cheng, Dr. Cathy Huang, and Dr. Tengfei Ma and colleagues trained mice to become heavy drinkers by repeated cycles of consumption and withdrawal of 20% alcohol — slightly higher than the average alcohol content in a glass of wine — and measured the effects on the balance of this delicate control of reward behavior.

    “To the best of our knowledge, this article demonstrated, for the first time, that excessive alcohol consumption suppresses activity of the No-Go pathway,” said Wang. By recording the activity of cells, the researchers found substantially increased GABA signaling, the primary inhibitory neurotransmitter of the brain, which quieted the No-Go pathway. Excessive alcohol consumption had the opposite effect in the Go pathway. These cells had increased glutamate signaling, the primary excitatory neurotransmitter in the brain, ramping up the Go signal.

    The findings reveal detailed information on the mechanisms underlying control of alcohol consumption. “Both of these effects serve to reinforce alcohol consumption, leading to pathological excessive use of alcohol,” wrote the authors.

    Through manipulation of cells specific to each pathway to mimic either increased glutamatergic or GABAergic activity, Cheng and colleagues confirmed that inhibition of cells in the No-Go pathway and excitation of cells in the Go pathway promotes alcohol consumption. The findings indicate that either of these alterations is sufficient to drive alcohol drinking behavior.

    The researchers dug deeper into the mechanism and found that activation of dopamine D2 receptors, the type that mediate the No-Go pathway, also reduced GABAergic activity and alcohol consumption. The regulation in GABAergic activity was mediated by a downstream target of D2 receptors called GSK3?, which altered the expression of GABA receptors in the cells.

    “These findings identified potential therapeutic targets,” said Wang, referring to GSK3? and GABA signaling in the No-Go pathway, which the researchers hope will aid development of new ways to treat alcohol abuse.

    The study may have even broader implications, according to Dr. John Krystal, Editor of Biological Psychiatry. “The balance between signaling in the [Go] and [No-Go] pathways is likely to be a critical factor influencing motivated behavior, generally. This balance might be targeted to treat alcoholism, but also other addictions, mood disorders, and perhaps OCD,” he said.


  10. Brain area involved in addiction activated earlier by cocaine consumption than thought

    June 6, 2017 by Ashley

    From the McGill University press release:

    Even among non-dependent cocaine users, cues associated with consumption of the drug lead to dopamine release in an area of the brain thought to promote compulsive use, according to researchers at McGill University.

    The findings, published in Scientific Reports, suggest that people who consider themselves recreational users could be further along the road to addiction than they might have realized.

    “The study provides evidence that some of the characteristic brain signals in people who have developed addictions are also present much earlier than most of us would have imagined,” says Marco Leyton, an expert on the neurobiology of drug use and addictions and professor in McGill’s Department of Psychiatry.

    Researchers have known for many years that cocaine use triggers the release of dopamine, a neurotransmitter involved in the brain’s reward system. In people with addictions, cues associated with drug use create the same effect. Visual cues — such as seeing someone using cocaine — are enough to trigger dopamine release and lead to craving.

    Scientists have long believed that, as addiction progresses, cue-induced release of dopamine shifts to the dorsal striatum, a structure deep inside the brain extensively studied for its role in the way we respond to rewards.

    “This area of the brain is thought to be particularly important for when people start to lose control of their reward-seeking behaviours,” Prof. Leyton says. “The dorsal part of the striatum is involved in habits — the difference, for example, between getting an ice cream because it will feel good versus being an automatic response that occurs even when it is not enjoyable or leads to consequences that you would rather avoid, such as weight gain or serious health hazards.”

    This switch from voluntary to habitual behaviour is thought to play an important role in the development of uncontrollable and compulsive drug use and the progression to addiction,” adds Sylvia Cox, a postdoctoral researcher at the McConnell Brain Imaging Center and the paper’s first author.

    To better understand how soon this effect might be seen, Professor Leyton’s team used positron emission tomography (PET) scans to look at what happens in the dorsal striatum of recreational cocaine users.

    The scientists created highly personalized cues by filming participants ingesting cocaine in the laboratory with a friend with whom they had used the drug before. During a later session, subjects underwent a PET scan while watching the video of their friend taking cocaine. Exposure to the cocaine-related cues increased both craving and dopamine release in the dorsal striatum.

    “An accumulation of these brain triggers might bring people closer to the edge than they had realized.” The findings also underscore the “importance of providing help early” to avoid the severe effects of dependency, he adds.