London: The feeling of euphoria, calmness and mental clarity experienced by some people after a long run or intense aerobic exercise may be driven by multiple brain systems, with the body's endocannabinoid system playing a key role, according to recent neuroscientific research.

For years, scientists believed that a "runner's high" was primarily caused by endorphins, the body's natural opioids released during physical stress to reduce pain. However, researchers now suggest that endorphins alone cannot fully explain the emotional and psychological effects of the phenomenon.

Endorphins circulating in the bloodstream have limited ability to cross the blood-brain barrier, meaning they may help reduce physical pain but cannot completely account for feelings of euphoria and emotional wellbeing.

Scientists have instead identified the role of endocannabinoids, naturally produced chemicals in the body that influence pleasure, memory, stress regulation and pain perception. One such chemical, anandamide, can easily cross the blood-brain barrier and activate receptors linked to emotion, motivation and reward.

Studies have found that prolonged aerobic exercise increases levels of anandamide, producing effects similar to the runner's high, including reduced anxiety, improved mood, lower pain perception and a sense of calm.

Researchers say endorphins may still contribute to the experience, but endocannabinoids appear to play a larger role in generating the emotional aspects of the phenomenon. Other brain chemicals, including dopamine, serotonin and noradrenaline, also contribute by influencing motivation, emotional balance, focus and reward.

Exercise also stimulates the production of brain-derived neurotrophic factor (BDNF), which supports brain connections and helps improve learning and memory.

The benefits of a runner's high extend beyond temporary pleasure, with exercise affecting stress regulation, inflammation, sleep quality, emotional processing and the brain's ability to adapt.

Studies suggest that moderate to vigorous aerobic exercise lasting about 30 to 60 minutes may increase endocannabinoid levels. However, the experience varies widely depending on factors such as genetics, fitness levels, sleep quality, psychological state and individual expectations.

Researchers note that even people who never experience a runner's high can gain significant mental health benefits from regular physical activity, including improved mood, cognition and resilience.