Even though marijuana’s effects are short-lived, its presence can be detected in the body for weeks, if not months. If you use marijuana regularly, the period of time active components and breakdown products remain in your system can range from a few hours to 90 days. Marijuana’s effects can differ from one individual to another. It’s possible for some people to feel ecstatic, while others may feel worried or paranoid. Others report feeling “dopey” and losing interest in tasks or being unable to grasp concepts as a result of depression. Tetrahydrocannabinol, often known as delta-9-THC or THC, is the ingredient in marijuana that makes you feel “high.”
THC has a cumulative impact. Someone who smokes multiple times over a period of several days has consumed a bigger THC dose and is, therefore, more likely to test positive than someone who smokes only once. The potency of each dose of THC and observer is also important to keep in mind. A person’s marijuana potency cannot be accurately determined without sophisticated laboratory equipment.
Tobacco smoke quickly absorbs THC into the bloodstream, where it’s dispersed throughout the body so that within thirty minutes, most of it is gone from the brain. They frequently occur within five to ten minutes of each other. Twenty-nine hours of THC is left in your system, but metabolites, including 11-hydroxy-delta-9-THC, are formed in the liver where they have a half-life of fifty hours.
About 25 to 30 percent of THC and its metabolites may remain in the body after one week. A strong dose of THC and its metabolites can take up to two or three weeks to eliminate from the body. Ingestion of THC results in far less THC reaching the brain, and it takes much longer for it to exert psychological effects.
In the hippocampus (see “Marijuana, Memory, and the Hippocampus”) and orbitofrontal cortex, THC affects memory formation and attentional concentration. Using marijuana impairs a person’s capacity to learn and complete complex tasks. Cerebellum and basal ganglia function are also disrupted by THC. These brain regions are responsible for balance, posture, and reaction speed. So, those who have used marijuana might not be able to drive safely, and they might have trouble playing sports or engaging in other physical activities (see “Does marijuana use affect driving?”).
Because THC activates the reward system in the brain, which includes regions that regulate the response to healthy pleasant behaviors like sex and eating, THC is a powerful anti-anxiety drug. THC, like most other drugs that individual’s abuse, activates neurons in the financial rewards, causing them to produce the signaling chemical dopamine at higher levels than are normally detected in response to natural pleasant stimuli.
Drivers who have been involved in fatal car accidents are most likely to have marijuana in their bloodstream. Two large European studies found that drivers with THC in their blood were roughly twice as likely as those who had not used drugs or alcohol to be at fault in a fatal incident.