By GLP-1 drugs, best known for helping patients lose weight and control blood sugar, may also be changing brain circuits tied to attention, emotion, motivation, and desire, according to emerging research.
The findings remain preliminary, and scientists caution that they do not yet know what the changes mean. But as tens of millions of people take medications such as semaglutide, sold as Ozempic and Wegovy, and tirzepatide, sold as Mounjaro and Zepbound, researchers are increasingly examining whether the drugs’ effects extend well beyond appetite.
In one study of adolescents and young women with a hormonal ovarian condition, researchers found notable changes in brain connectivity after several months of treatment. Allison Shapiro, an assistant professor at the University of Colorado Anschutz, reviewed brain scans taken before and after the drugs were used and said the results were unexpected.
“We didn’t expect to see this effect, and we really don’t know what it means,” Shapiro told The Washington Post.
The changes appeared in the salience network, a system involved in directing attention. The medications were developed to mimic gut hormones that help regulate blood sugar and appetite, but evidence now suggests they may also affect broader central nervous system activity.
Some scientists have described the widespread use of GLP-1 drugs as one of the largest unintended experiments in neuroscience. Researchers are studying whether the medications could help treat addiction, cognitive decline, mood disorders, and other conditions.
GLP-1 hormones and their receptors are not confined to the digestive system. They also appear in the heart and in multiple brain regions. Researchers are still studying whether the relatively large drug molecules cross the blood-brain barrier directly, or whether some effects occur indirectly through reduced inflammation, improved metabolic health, or signals traveling from the gut to the brain along the vagus nerve.
Studies suggest the drugs may quiet overactive immune responses in the brain, which can contribute to long-term damage, while also supporting neuron function and resilience.
Physician-scientist Lorenzo Leggio, clinical director and deputy scientific director at the National Institute on Drug Abuse, has studied the medications’ possible use in addiction treatment for years. His interest grew out of early animal studies showing that GLP-1-like compounds reduced alcohol consumption.
Leggio’s team uses controlled settings, including simulated bars and virtual reality scenarios, to examine how the drugs affect responses to cues tied to cravings for alcohol, food, and other stimuli. The medications appear to influence dopamine-related reward pathways and may also affect the amygdala, the brain region involved in processing fear, stress, and other emotions.
“It’s very exciting times, but we don’t fully understand how it works,” Leggio said.
Many users report that the drugs sharply reduce intrusive thoughts about food. But that same dampening of reward circuits could also affect other drives.
“If you think about it from a survival standpoint, some of the foundational behavior such as eating and sex could be impacted,” Leggio said.
He added that regulators at the Food and Drug Administration have reviewed safety data and have not identified that as a common issue.
Some patients have reported mental cloudiness or emotional blunting, including less enjoyment, lower motivation, and diminished interest in social or intimate activity. Those reports have raised questions about whether the drugs, in some patients, may move beyond curbing harmful impulses and begin affecting core aspects of personality.
Research into GLP-1 drugs and neurodegenerative disease has produced mixed results. Hopes that the medications might slow Alzheimer’s disease suffered a setback when a large Phase III trial by Novo Nordisk failed to show meaningful improvement in cognitive or functional decline. Still, an analysis of trial data found modest positive changes of about 10 percent in certain biomarkers tied to inflammation and brain-cell damage, according to Aaron Burstein of the Alzheimer’s Drug Discovery Foundation.
Earlier imaging research had suggested the drugs might help preserve brain volume in regions involved in planning, memory, and emotion. Some experts now believe the medications may need to be studied earlier in the course of disease, before advanced decline has taken hold.
Similar questions surround Parkinson’s disease. Animal studies have been promising, but human trials have been less conclusive. Researchers are considering whether higher doses or earlier treatment might produce clearer results.
Interest is also growing in psychiatric uses. Some clinicians have reported anecdotal improvements in mood, anxiety, and compulsive symptoms among patients who took GLP-1 drugs for metabolic reasons.
Researchers have begun studying possible benefits for schizophrenia, both to manage side effects of other medications and to examine whether GLP-1 drugs directly affect brain communication and inflammation. Other work is exploring whether the drugs could help with lingering symptoms after COVID-19 infection.
Some of the clearest evidence of brain changes has come from research on polycystic ovary syndrome, also called polyendocrine metabolic ovarian syndrome, which affects roughly one in 10 U.S. women and involves hormonal and metabolic disruption.
In trials at the University of Colorado Anschutz led by pediatric endocrinologist Melanie Cree, brain imaging by Shapiro’s team found increased connectivity in certain areas. Those changes may be linked to the hypothalamus, a brain region rich in GLP-1 receptors that helps regulate hunger, hormones, stress, and sleep.
Researchers emphasized that the work is still preliminary. The questions are especially important for adolescents, whose brains are still developing and may respond differently than adult brains. Effects that reverse quickly in adults could potentially last longer in younger patients.
“The real test is how the brain effects are sustained when you take adolescents off the drugs,” Shapiro told The Washington Post.
Grace Hamilton, 28, who lives near Denver, lost more than 100 pounds on the medications and saw her testosterone levels normalize. She has remained on treatment and says she no longer needs antidepressants she had taken since her teenage years. She also says her interest in alcohol has disappeared.
“I would probably stand to bet it’s not just a coincidence,” Hamilton explained.
For now, scientists say the drugs’ promise is substantial, but so is the need for caution. Long-term studies will be needed to determine whether GLP-1 medications can be safely used to treat neurological and psychiatric conditions, and whether their effects on the brain carry unintended consequences that are only beginning to come into view.
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