Delta-9-tetrahydrocannabinol (THC), the primary intoxicating compound in cannabis, produces a distinct physiological effect called THC-induced hypothermia. This phenomenon is a temporary and measurable reduction in the core body temperature following ingestion. The effect is consistently observed across various species in preclinical research, establishing it as a fundamental pharmacological property of THC. This temperature change is strongly dose-dependent; a greater amount of THC typically leads to a more pronounced cooling effect.
The Basics of Mammalian Thermoregulation
Maintaining a stable internal temperature, a process known as thermoregulation, is a fundamental function necessary for the body’s survival. This complex process is governed by the central nervous system, which acts like a precise thermostat to keep the body within a narrow temperature range. Sensory inputs from the skin and deep body tissues constantly feed temperature data back to the brain.
When the body needs to warm up, it can trigger involuntary responses like shivering, which generates heat through muscle activity. It also activates thermogenesis in specialized tissue, such as brown adipose tissue, to produce heat without shivering. Conversely, to cool down, the brain instructs blood vessels near the skin to widen, a process called vasodilation, allowing heat to radiate away from the body.
The Mechanism of THC’s Action on Temperature
THC-induced hypothermia stems from the compound’s direct interaction with the body’s internal regulatory system. The mechanism is centered on the activation of the cannabinoid receptor type 1 (CB1 receptor). This receptor is a major component of the endocannabinoid system, which naturally helps modulate various functions, including temperature control. THC mimics the body’s own cannabinoids and binds powerfully to these CB1 receptors.
These receptors are densely concentrated in the brain region responsible for thermoregulation, the hypothalamus, particularly within the preoptic area (POA). The hypothalamus maintains a specific thermal set-point, which is the internal temperature the body attempts to defend. When THC activates the CB1 receptors in this area, it effectively lowers this set-point.
In response to this artificially lowered set-point, the brain triggers heat-dissipating behaviors. It suppresses internal heat production mechanisms, such as thermogenesis and shivering, and initiates cooling responses like vasodilation. This physiological cascade leads to an accelerated loss of heat from the body core, manifesting as hypothermia. The cooling effect can be blocked by administering a CB1 receptor antagonist, confirming the receptor’s direct involvement.
Potential Therapeutic Applications
The controlled ability of THC to temporarily lower core body temperature has captured the attention of researchers for its potential medical utility. Induced hypothermia is a medically recognized treatment, particularly in neuroprotection, where slight cooling of the brain can limit damage after severe injury. The reduced temperature slows the brain’s metabolic rate, decreasing the demand for oxygen and nutrients in damaged tissue.
This deliberate cooling is used in clinical settings following events like cardiac arrest, stroke, or traumatic brain injury. THC and its related compounds offer a pharmacological method to induce this protective hypothermia. Drug-induced cooling could offer a less invasive and more easily managed alternative to external cooling methods.
Scientists are exploring specialized cannabinoid analogs that can selectively trigger the hypothermic effect without causing the psychoactive effects associated with THC. The goal is to isolate the specific temperature-regulating pathway through the CB1 receptor to create novel neuroprotective agents. Preclinical experiments have shown that drug-induced hypothermia can alleviate brain damage and reduce neurological deficits, potentially leading to new therapeutic strategies for central nervous system injuries.