Can a brain scan reveal whether a young teen is more or less likely to engage in problematic drug use in the future? Results from a new study suggest there are neural markers predictive of this risk.
The study, conducted by researchers from Stanford, analyzed MRI data from 144 teenagers at the age of 14, who had never engaged in recreational drug use before. While their brains were being imaged, the teens were simultaneously assessed with behavioral tests called “Monetary Incentive Delay Tasks.” Essentially, the teens played video games for points, which can later be exchanged into money. Such test allows the researchers to measure impulsivity, novelty seeking, and reward processing.
"We wanted to know whether reward anticipation brain activity at age 14 would predict later substance use in risk kids – who are high novelty seekers," said Brain Knutson, from Stanford University, a professor of psychology at Stanford, and co-director of the Stanford Neurosciences Institute’s NeuroChoice program.
Ironically, teens who showed less brain engagement at the prospects of monetary reward were at higher risks for drug use later on. "We found that at age 14, high novelty seekers who had less of a neural response to anticipated reward were more likely to use substances at age 16,” Knutson explained.
The brain areas under scrutiny included the mesolimbic (ventral striatal and midbrain) and prefrontal cortical (dorsolateral prefrontal cortex) regions. But why less activity in these areas would correlate with higher impulsivity, the researchers don’t exactly know yet. "It could be due to inheritance, environmental influences, or (most likely) a combination of the two," said Knutson. They hypothesize that those who show less motivation towards traditional rewards like money may have a higher propensity for unconventional rewards like drugs.
"What the neural marker does tell us is that they likely are motivated less (not more) by conventional rewards," said Knutson. "This might suggest that interventions for these kids might target more powerful but alternative rewarding activities."
Indeed, the team hopes that with more work, the scan can be used to help physicians identify vulnerable teenagers at an early point when interventions may be more effective. But more studies are required to confirm the validity of these neural markers before this tool can be used in clinical settings.
Additional sources: Stanford University, Wired, BBC