New research found that individuals with anorexia nervosa have elevated opioid neurotransmitter activity, which may contribute to appetite loss and emotional symptoms.
A study from the Turku PET Centre in Finland suggests that alterations in opioid neurotransmitter function in the brain may play a key role in anorexia nervosa.
Anorexia nervosa is a severe psychiatric disorder characterized by restrictive eating, an intense fear of weight gain, and distorted body image. It can lead to serious complications, including malnutrition, depression, and anxiety. The study’s findings highlight how disruptions in neurotransmitter activity may contribute to the development and persistence of the disorder.
“Opioid neurotransmission regulates appetite and pleasure in the brain. In patients with anorexia nervosa, the brain’s opioidergic tone was elevated in comparison with healthy control subjects. Previously we have shown that in obese patients the activity of the tone of this system is lowered. It is likely that the actions of these molecules regulate both the loss and increase in appetite,” says Professor Pirjo Nuutila from the University of Turku, Finland.
Brain Energy Consumption in Anorexia
In addition, the researchers measured the brain’s glucose uptake. The brain accounts for about 20% of the body’s total energy consumption, so the researchers were interested in how a reduction in the energy intake affects the brain’s energy balance in anorexia.
“The brains of patients with anorexia nervosa used a similar amount of glucose as the brains of the healthy control subjects. Although being underweight burdens physiology in many ways, the brain tries to protect itself and maintain its ability to function for as long as possible,” says Professor Lauri Nummenmaa from Turku PET Centre and continues:
“The brain regulates appetite and feeding, and changes in brain function are associated with both obesity and low body weight. Since changes in opioid activity in the brain are also connected to anxiety and depression, our findings may explain the emotional symptoms and mood changes associated with anorexia nervosa.”
Reference: “Anorexia nervosa is associated with higher brain mu-opioid receptor availability” by Kyoungjune Pak, Jouni Tuisku, Henry K. Karlsson, Jussi Hirvonen, Eleni Rebelos, Laura Pekkarinen, Lihua Sun, Aino Latva-Rasku, Semi Helin, Johan Rajander, Max Karukivi, Pirjo Nuutila and Lauri Nummenmaa, 12 January 2025, Molecular Psychiatry.
DOI: 10.1038/s41380-025-02888-3
The study was carried out in collaboration with the Turku University Hospital and Pusan National University in South Korea. The brains of patients with anorexia nervosa and the healthy control subjects were imaged using positron emission tomography at Turku PET Centre.
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