Size of Brain’s ‘Pleasure Center’ Predicts Teen Substance Use
Significant numbers of American teenagers use marijuana, alcohol or other substances on a monthly or yearly basis. In a study published in February 2015 in the journal Social Cognitive and Affective Neuroscience, researchers from one U.S. institution and one Dutch institution explored the role that sensitivity to the rewarding effects of substance use plays in teen drug/alcohol consumption. These researchers concluded that adolescents whose brains grow increasingly sensitive to rewarding sensations have heightened odds of beginning substance use and/or boosting their rates of alcohol intake.
Teens and Substance Use
Current data compiled by the University of Michigan and the National Institute on Drug Abuse indicate that teenagers in the U.S. are substantially reducing their involvement in alcohol consumption and cigarette use. Between the years 2013 and 2014, American teens also slightly reduced their average monthly intake of marijuana, the nation’s most popular recreational drug. Despite this fact, over one-fifth of all high school seniors still consume marijuana or some other form of cannabis every month; over a third of seniors consume the drug at least once a year. Tenth-graders have lower monthly and yearly rates of marijuana/cannabis use than their older counterparts. Eighth-graders have even lower monthly and yearly rates of intake.
Other drugs that are relatively popular targets of use/misuse among adolescents include synthetic marijuana, amphetamine-based and non-amphetamine based stimulants normally prescribed for the treatment of ADHD (attention-deficit hyperactivity disorder), prescription opioids, dextromethorphan-containing cough syrups and sedative-hypnotic medications (tranquilizers and sedatives). In addition, a small but significant number of younger teenagers consume makeshift drugs that fall into a broad category of substances known as inhalants. Despite long-term reductions in yearly and monthly intake, alcohol remains the most popular substance among both younger and older teens.
Substance Use and Reward Sensitivity
All humans register rewarding sensations in a part of the brain known informally as the pleasure center. Normally, the source of these sensations is activity that in some way promotes survival or general well-being (e.g., eating food or having sex). However, consumption of alcohol and a vast range of drugs/medications also triggers rewarding feelings in the pleasure center. Unfortunately, the amount of reward gained from substance use can be drastically higher than the amount of reward gained from life-sustaining daily activity. This heightened level of reward largely helps explain patterns of repeated substance intake that end with the onset of physical dependence and/or substance addiction. Broadly speaking, people who perceive drug or alcohol consumption as a particularly rewarding sensation have increased odds of developing diagnosable substance problems.
Impact of Increasing Sensitivity
In the study published in Social Cognitive and Affective Neuroscience, researchers from the University of Minnesota-Twin Cities and the Netherlands’ Erasmus Medical Center-Sophia Children’s Hospital used information gathered from a group of teenagers between the ages of 15 and 18 to gauge the impact that reward sensitivity has on the average adolescent’s chances of using drugs or alcohol. At the time the study began, none of these teens had a history of involvement in drug or alcohol intake. Two years later, the researchers looked for the initiation of regular drinking or any amount of drug use among the participants. The researchers also conducted before-and-after testing of the teenagers’ sensitivity to rewarding sensations.
After analyzing the data, the researchers concluded that the teenagers who became increasingly sensitive to rewarding sensations in their pleasure centers had significantly higher chances of getting involved in substance use than their counterparts who did not experience increasing reward sensitivity. In addition, they linked a boost in reward sensitivity to the frequency of alcohol intake in the participants. As part of their work, the researchers also looked at the size of a structure in the pleasure center called the left nucleus accumbens. They concluded that teens with relatively small versions of this brain structure have heightened risks for involvement in drug/alcohol use.
The study’s authors believe that their findings help illustrate the link between adolescents’ substance intake and the amount of reward such intake produces inside the brain. They also believe that their findings illustrate the potential impact of the size of the pleasure center’s structures on teens’ chances of consuming alcohol or drugs.