Why your eyes turn red (and why you won't overdose)

Society · Published 19 October 2026 Swipe more like this →

In short: Marijuana interacts with your body's internal chemistry in ways that range from simple physical reactions to complex neurological shifts. While pop culture often focuses on the 'high,' the underlying mechanisms involve your endocannabinoid system—a network that naturally regulates everything from your mood to your appetite.

The physical sensations of marijuana use are primarily driven by cannabinoids, specifically delta-9-tetrahydrocannabinol (THC). When consumed, THC enters the bloodstream and binds to cannabinoid receptors throughout the body. This system naturally regulates memory, mood, and appetite; however, external cannabinoids 'overly activate' these receptors, leading to the characteristic psychoactive effects. The experience is highly variable, influenced by genetics, age, sex, the specific strain used, and the method of consumption. For instance, smoking allows THC to pass quickly from the lungs to the brain, while ingestion takes 30 minutes to an hour for absorption.

Short-term physical effects are well-documented but vary by individual. Common reactions include bloodshot eyes—caused by the opening of capillaries—and dry mouth. Other effects include increased heart rate, drowsiness, and muscular incoordination. While some users experience euphoria, others may face anxiety, dizziness, or impaired judgment. Notably, high doses can lead to more intense reactions like hallucinations or psychosis. However, research consistently shows that marijuana does not cause cancer, and there is no evidence that it causes schizophrenia in individuals who were not already predisposed to the disorder.

Safety and long-term impacts remain a primary focus of ongoing research. While no one has ever overdosed on medical cannabis, high doses of THC can lead to 'cannabis hyperemesis syndrome,' characterized by severe vomiting. Long-term use, particularly during adolescence, may affect brain development and increase the risk of depression in young adulthood. Furthermore, smoking the substance can cause lung and blood vessel damage, increasing risks for heart disease and stroke. Despite these risks, the substance is frequently utilized medically to manage conditions like epilepsy, inflammation, and neuropathic pain.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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