PITTSBURGH -- What makes some teenagers more likely to experiment with drugs and alcohol? A new study from Pitt theorizes that one factor may be tied to their levels of dopamine, also known as “the pleasure chemical.”

The study, published in the journal Nature Communications, analyzed a massive data set that followed substance use levels in a group of subjects aged 12 to 30. The data set, from the National Consortium on Alcohol and Neurodevelopment in Adolescence, is from more than 800 subjects from five sites around the country, including Pittsburgh.

Pitt researchers divided substance use patterns into four categories, including a “youth peak,” with high substance use levels in adolescence that declined into adulthood (26% of participants); “no/low use” throughout both adolescence and adulthood (30%); “adolescent increasing,” with substance use beginning in adolescence and increasing through adulthood (17%); and “adult increasing,” with low substance use in adolescence that increases into adulthood (26%).

In the youth peak grouping, in particular, the Pitt researchers found that levels of dopamine were low as they entered adolescence.

“People think higher dopamine means more risk-taking,” said Ashley Parr, lead author of the study and research assistant professor of psychiatry at Pitt. “This really kind of challenges a common assumption. The way we were thinking about it is that teens who are entering adolescence with low dopamine may be engaging with substances as a means of boosting dopamine, getting that sensation, seeking boost.”

Researchers were able to measure dopamine levels in the subjects over a period of nine years, using brain tissue iron as a proxy for dopamine levels — a technique pioneered at Pitt.

Across all of the substance use groups, people with low dopamine levels had more substance use behavior.

There has long been a scientific association between depressed dopamine levels and alcohol use, said Parr, but the causation wasn’t clear, and researchers speculated that alcohol use was lowering dopamine levels over time.

This research is the first to show in humans that the causation might run the other way, she said: that the dopamine levels might be lower from the start.

“The critical point is that these differences were detectable early in adolescence, before substance use occurred,” she said. “For us, this was kind of surprising.”

Researchers also found that dopamine levels increased more rapidly in the “youth peak” category than in other groups, catching up to the other groups in their mid to late 20s. That is also the age when substance use in the youth peak grouping started to decline.

In the future, Parr hopes to study the association between dopamine levels in teenagers and a different type of dopamine booster: screen time.

“What are modern-day behaviors that teens are engaging with that can easily boost dopamine levels?” she said. “Instagram, TikTok. And, unlike substances, those are always accessible. I want to see if these same biological indicators are driving other reward behaviors.”

She is also interested in probing earlier childhood to investigate why some pre-teens have lower dopamine levels entering adolescence than others.

And she is reframing risk-taking as a fundamental part of adolescence — even as something parents can encourage through youth sports or other positive social outlets.

“Risk-taking is a normal part of being a teenager,” she said. “It’s healthy, part of being an adolescent.”

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