By Stephen Beech
Teenagers get hooked on drugs because their brains are wired differently, suggests a new study.
Many differences appeared to exist in the brain structure of adolescents before any substance use – pointing to the role it may play in drink and drug abuse, say scientists.
The study of nearly 10,000 teenagers identified distinct differences in the brain structures of those who used substances before the age of 15 compared to those who did not.
Many of the structural brain differences appeared to exist in childhood before any substance use, which the research team says suggests they may play a role in the risk of substance use initiation later in life, in tandem with genetic, environmental, and other neurological factors.
Dr. Nora Volkow, director of the National Institute on Drug Abuse (NIDA), based in Maryland, said: “This adds to some emerging evidence that an individual’s brain structure, alongside their unique genetics, environmental exposures, and interactions among these factors, may impact their level of risk and resilience for substance use and addiction.
“Understanding the complex interplay between the factors that contribute and that protect against drug use is crucial for informing effective prevention interventions and providing support for those who may be most vulnerable.”
Among the 3,460 adolescents who initiated substances before age 15, most (90.2%) reported trying alcohol, with considerable overlap with nicotine (61.5%) and/or cannabis (52.4%).
The research team found that substance initiation was associated with a variety of brain-wide as well as more regional structural differences primarily involving the cortex, some of which were substance-specific.
The study, published in JAMA Network Open, used data from the Adolescent Brain Cognitive Development (ABCD) Study of brain development and health in children and adolescents in the United States.
Researchers from Washington University in St. Louis assessed MRI scans taken of 9,804 children across the U.S. when they were aged nine to 11 at the outset, and followed them over three years to determine whether certain aspects of brain structure captured in the initial MRIs were associated with early substance use.
They monitored for alcohol, nicotine and cannabis use, as they are the most common substances used in early adolescence, as well as the use of other illicit substances.
The research team compared MRIs of 3,460 participants who reported substance initiation before age 15 from 2016 to 2021 to those who did not (6,344).
They assessed both global and regional differences in brain structure, as well as looking at measures including volume, thickness, depth of brain folds, and surface area, primarily in the brain cortex.
The cortex is the outermost layer of the brain, tightly packed with neurons and responsible for many higher-level processes, including learning, sensation, memory, language, emotion, and decision-making.
Specific characteristics and differences in those structures – measured by thickness, surface area, and volume – have been linked to variability in cognitive abilities and neurological conditions.
The research team identified five brain structural differences at the global level between those who reported substance initiation before the age of 15 and those who did not.
These included greater total brain volume and greater subcortical volume in those who indicated substance initiation.
An additional 39 brain structure differences were found at the regional level, with around 56% of the regional variation involving cortical thickness.
Some brain structural differences also appeared unique to the type of substance used.
Analysis showed that many of the brain differences still held even after removing participants who reported substance initiation before the study began.
The resulting comparison was between those who did not report any substance use initiation and a subgroup of 1,203 participants in the substance use initiation group who did not have any substance use experience when their MRIs were first captured.
The research team said that the results of the secondary analysis suggest that some of the brain structural differences may exist prior to any substance use, challenging the interpretation that such differences are only driven by substance exposure and pointing to an area for further investigation.
The team says future studies will be “crucial” to determine how initial brain structure differences may change as children age and with continued substance use or development of substance use disorder.
Study corresponding author Dr. Alex Miller, an Assistant Professor of Psychiatry at Indiana University said: “Through the ABCD study, we have a robust and large database of longitudinal data to go beyond previous neuroimaging research to understand the bidirectional relationship between brain structure and substance use.”
He added: “The hope is that these types of studies, in conjunction with other data on environmental exposures and genetic risk, could help change how we think about the development of substance use disorders and inform more accurate models of addiction moving forward.”
While the data could someday help inform clinical prevention strategies, the research team emphasizes that brain structure alone cannot predict substance use during adolescence and that the findings should not be used as a diagnostic tool.
