Teenagers who smoke weed, drink alcohol or vape before their 15th birthday have a different brain structure from those who do not, a study has found.
Researchers at Indiana University tracked nearly 10,000 adolescents for two years, of which 35 percent self-reported consuming any alcohol, marijuana and/or nicotine before age 15.
All participants also underwent brain scans that revealed those who had used any of the substances before 15 had a thinner prefrontal cortex — an area of the brain linked to regulating emotions — compared to those who said they had not used drugs or alcohol at a young age.
Those who said they had used substances young also tended to have larger brains overall and a greater subcortical volume, the area of the brain linked to memory, emotion, pleasure and hormone production.
Scientists said it was not clear whether the substances altered the teenager’s brains or if teens with certain brain characteristics were predisposed to try substances.
The researchers concluded that varying brain structures may reflect a predisposition teens have for engaging in substance use earlier in life, which could have ‘potential cascading implications for development of later problems.’
Dr Nora Volkow, director of the National Institutes of Drug Abuse (NIDA), 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.’
Teenagers who smoke weed, drink alcohol or vape before their 15th birthday have a different brain structure from those who do not, a study has found (stock image)
For the study, published this month in JAMA Network Open, children were recruited from the Adolescent Brain and Cognitive Development study (ABCD study).
Set up by the NIDA, the study aims to analyze the development of children’s brains and how this may be affected by certain factors — including drug abuse.
For the current paper, children were recruited from 22 locations across the US and were nine years old at the start of the study.
They were tracked from June 1, 2016 to October 15, 2018 and asked to self-report whether they had used any substances.
Among the 3,460 respondents who admitted to using substances before their 15th birthday, alcohol was the most common substance used — with 90 percent reporting this.
About 62 percent of participants also reported using nicotine, while 52.4 percent said they had used marijuana before 15.
In the analysis, adjusted for factors including gender, the researchers identified five key differences across the whole brain between the two groups — including differing overall brain size.
These were that teenagers who said they had used substances were more likely to have a thinner prefrontal cortex overall, but a thicker cortex in all other lobes such as the occipital lobe — the area of the brain linked to visual perception, including color, form and motion.
Results also showed they had a larger brain, a larger globus pallidus — a structure which regulates voluntary movements — and a larger hippocampus — an area of the brain that helps with learning and memory.
At the regional level, they also identified 39 differences between the two groups — with about 56 percent of this linked to cortical thickness.
Of these, 22 of them — or 56 percent — were linked to variations in cortical thickness, with the cortical being the brain’s outer layer and important for higher-level processing, such as for language, memory and reasoning.
There were also some differences depending on the substance used, with those who used cannabis having lower right caudate volume — an area linked to processing visual information.
The researchers wrote in the study: ‘Our findings suggest that structural differences in the prefrontal cortex may predispositionally contribute to initial stages of substance involvement.
‘Our data cannot yet determine at what developmental point(s) substance-related variability in brain structure arose.
‘Large-scale longitudinal studies… tracking neurodevelopment and substance exposure or involvement from the neonatal period to young adulthood are necessary to address the origins of these differences.’
The rate at which teens are using substances has experts concerned over concerns of the effects on brain development.
Previous research has shown excessive alcohol consumption in teenagers, or binge drinking, stunts the growth of areas of the brain linked to impulse control, memory and learning and can also leave them at higher risk of depression.
Smoking marijuana at a young age can also affect how the brain builds connections and thickens grey matter, which could cause lifelong problems with memory, attention and learning.
There have also been suggestions that vaping nicotine could raise someone’s risk of dementia by narrowing the blood vessels supplying the organ.
Researchers of the studied published this month hope the data could be used to help identify those at risk of substance addiction early on and prompt quick interventions.
