A specialist involved in research into the effects of GLP-1 medications on the brain has shared a serious warning.
GLP-1 drugs were first approved to help treat diabetes, but they have more recently surged in popularity as weight loss treatments. These medications, including semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), now represent one of the fastest-growing segments of the pharmaceutical market, with between 20 to 25 million patients currently using these therapies worldwide.
These medications work by using hormones to help regulate blood sugar, while also helping people feel satisfied after eating smaller amounts. Recent clinical trials have demonstrated that these medications can lead to 10–20% reductions in body weight, alongside meaningful improvements in blood pressure, cholesterol levels, and inflammatory markers.
When paired with nutritious eating habits and consistent exercise, GLP-1 treatments can support weight loss, which has helped drive their growing demand. Beyond weight management, emerging research shows that GLP-1 therapies may also provide cardiovascular and kidney protection, with major clinical trials reporting reductions in heart attacks, strokes, and cardiovascular mortality among high-risk patients.
Among the experts studying their broader impact is psychiatrist Dr Riccardo De Giorgi, a University of Oxford researcher examining how GLP-1 drugs influence the brain. De Giorgi’s work focuses on experimental medicine studies for the repurposing of drugs with immuno-metabolic activity in mental disorders, looking at early markers of response such as neuropsychological changes and reward processing.
At Oxford, researchers recruited 70 volunteers and asked them to complete computer-based tasks one week after receiving an injection. The exercises were designed to measure motivation and the desire to achieve rewards, giving scientists a way to track changes in reward processing.
Although the complete findings have not yet been published, Dr De Giorgi said there may be “quite convincing evidence” that a single dose can alter the brain’s reward system, according to BBC Science Focus. This follows recent neuroscientific research published in Nature in 2026 showing that GLP-1 drugs engage a discrete neural circuit linking the hindbrain, central amygdala, and dopamine neurons, which selectively suppress the consumption of palatable foods by reducing dopamine release in the reward center of the brain.
Some earlier research has indicated that GLP-1 drugs may reduce cravings for addictive substances, including alcohol and nicotine, possibly by dampening the dopamine-based reward response in the brain. A 2025 clinical trial from a US team demonstrated that semaglutide reduces alcohol cravings as well as the amount that heavy drinkers consume on their drinking days. However, much of that work has been carried out in mice and rats, meaning human evidence remains limited.
At the same time, researchers are increasingly exploring whether these medications could help address a range of neurological conditions, including depression and dementia. A comprehensive analysis published in Nature Mental Health in 2025 found promising but still preliminary evidence that GLP-1 medications could be beneficial across a range of cognitive and mental health disorders. Research is also underway to investigate their potential in Parkinson’s disease, with some trials showing more encouraging results than others.
However, emerging research also highlights potential neurological side effects that warrant monitoring. A 2025 pharmacovigilance analysis published in Scientific Reports identified 19 distinct neurological adverse event signals associated with GLP-1 drugs, including dizziness, tremor, taste disorders, lethargy, and tingling sensations. The analysis found that 45% of these neurological adverse events occurred within 30 days of treatment initiation. Additionally, about 50% of patients who discontinue GLP-1 therapy do so because of adverse side effects, according to the National Institute on Drug Abuse.
Some patients report experiencing emotional blunting or anhedonia—a reduced ability to experience pleasure—though the mechanism and prevalence of this effect remain unclear. De Giorgi notes that while some people report such effects, individual responses vary significantly, and more research is needed to understand why certain patients experience these symptoms while others do not.
Requests for comment were sent to Novo Nordisk and Eli Lilly and Company.
The warning comes amid wider discussion about how these injections should be dosed. Dr. Dean Jones, DC, recently spoke about the common advice to follow a fixed schedule that typically increases the dose every four weeks, as reported by MedExpress.
Jones challenged that approach, arguing that many patients are moved through treatment without enough direct medical follow-up.
“A lot of people get these medications through high-volume operations with almost no clinical contact, where one physician signs off on thousands of patients and nobody ever asks how it’s going.
“Without that conversation, the schedule becomes the plan by default, and people climb toward the maximum whether they need it or not.”
He said clinicians should pay close attention to a crucial stage of treatment rather than focusing only on scheduled dose increases.
“The point where the constant thinking about food quiets down and cravings settle, but a person can still eat normally and get on with their day,” he explained.
“Past that point, more medication doesn’t buy much and costs plenty.”
The GLP-1 market landscape has shifted significantly in 2026, with Eli Lilly’s tirzepatide products gaining substantial market share from Novo Nordisk’s semaglutide offerings. Eli Lilly’s dual GLP-1/GIP receptor mechanism delivers superior weight loss—around 20% in trials compared to semaglutide’s 14%—helping propel the company into market leadership. Eli Lilly has overtaken Novo Nordisk in the global GLP-1 market share outside the United States, with tirzepatide generating stronger sales momentum internationally.