Marijuana use has been linked to a range of cognitive impairments, including difficulty with learning and performing complex tasks. This is due to the way THC, the main active component of cannabis, interacts with the central nervous system (CNS). THC alters the functioning of the cerebellum and basal ganglia, areas of the brain responsible for balance, posture, coordination and reaction time. At a cellular level, THC inhibits adenylate cyclase, suppresses calcium and sodium channels, and activates mitogen-activated protein (MAP) kinase enzymes.
The effects of THC extend throughout the CNS. It is believed to reduce pain and inflammation, as well as help control spasms and seizures. However, there are potential long-term negative effects on the CNS that must be taken into account. A recent study found that genetic predisposition and exposure to THC can synergistically activate NF-kB-Cox-2 signals in astrocytes.
These deficiencies are usually associated with excessive drug use over a long period of time and are unlikely to affect most recreational users. THC is difficult to administer intravenously, but some studies have been successful in doing so at doses comparable to those found in human cannabis users. Cannabis varieties high in CBD do not activate receptors in the endocannabinoid system like THC does, but instead act on organs and systems related to immune and inflammatory responses. Exogenously administered cannabinoids like THC cannot mimic the physiological effects of locally released endocannabinoids.
Medical cannabis has been used to treat a wide range of disorders, much of which is attributed to its interaction with the CNS. However, research with mice without CB1 receptor activation suggests that not all antinociceptive effects of THC or anandamide are mediated by CB1 receptors. Synthetic cannabinoids are more soluble in water than THC, which makes intravenous administration easier. Studies have shown that drug-induced effects on cognitive performance can persist for up to one week after stopping taking the medication, possibly due to the persistence of THC in the body or a subtle withdrawal syndrome.
The time it takes for THC plasma concentrations of 11-OH-THC and THCCOOH to reach their maximum levels after smoking is 8, 15 and 81 minutes respectively. THC or cannabis extracts can also be taken orally in fat-containing foods or dissolved in a suitable pharmaceutical oil, but absorption is delayed and variable. THC acts as a partial agonist of the cannabinoid receptor CB1 (mainly found in the brain and spinal cord), as well as CB2 receptors expressed in cells of the immune system. There are also artificial synthetic cannabinoids available that are more potent and more soluble in water than THC. This explains why THC has psychoactive effects unlike other cannabinoids; when it enters the body it mainly affects neurological centers.