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Tetrahydrocannabinol (THC) is the main active ingredient derived from the flower and leaves of the Cannabis sativa plant. It is also known as Marijuana, Pot, Grass, Weed or Ganja, and when extracted as a resin it is referred to as Hashish or Hash. It is most commonly smoked but can also be ingested. It is used for its ability to produce a calming effect, a euphoric or giddy mood, and heightened sensory experiences.

American statistics show that close to 50% of people will try cannabis - making it the most widely used of the illicit drugs - and of these about 9% go on to develop cannabis abuse or dependence at some point in their lives [ref]. Cannabis has been labelled as a "gateway drug" because its use is associated with increase risk of abuse or dependence upon other substances [ref].

How Cannabis Works

After being smoked the effects of cannabis begin to be felt in minutes, and if ingested this takes about 30 minutes. The effects then last 2 - 4 hours, though there can be some lingering effects for up to 12 hours. Cannabis can be detected in the urine up to a week after a single use, and up to 30 days after chronic use. Hair samples can also be used to detect Cannabis consumption within 3 months of using.

Cannabinoid receptors exist in the brain and various other body organs, and cannabis has its effect when THC binds to these receptors. The role of cannabinoid receptors in the brain remains incompletely understood, but stimulating them seems to reduce pain perception, and they also interact with various major neurotransmitter systems, such as opioid receptors, monoamines and GABA.

Regular Cannabis Use

In some parts of the world, cannabis use has been legalized and is used recreationally. Cannabis has also been found to have certain medicinal properties, such as reducing pain, alleviating nausea, increasing appetite and easing muscle cramps and spasms, and has been shown to be effective for treating these symptoms in conditions such as cancer, Multiple Sclerosis, and AIDS. It can also be used to treat Glaucoma. When used for medical purposes, cannabis is usually prescribed in pill form.

Cannabis Intoxication

Although cannabis usually produces a calming, euphoric or detached feeling, it can also induce states of anxiety, panic and even paranoid delusions. Cannabis also causes perceptual changes, where colors seem brighter, music more vivid, emotions more poignant, and time seems to go more slowly. At high doses hallucinations can occur.

Cannabis impairs concentration, reduces mental alertness, slows one's reaction time and worsens coordination. For these reasons, it is dangerous to drive or operate heavy machinery when under the influence of this drug.

Cannabis also causes various physical symptoms such as decreased blood pressure and an accelerated heart beat, increased appetite and dry mouth. For some individuals with heart conditions the lowered blood pressure and increased heart rate may be dangerous and even life-threatening, but otherwise cannabis does not pose any dangers from overdose.

Effects of Long-Term, Heavy Cannabis Use

Long-term, heavy cannabis use can lead to on-going problems with attention and concentration, short-term memory, and the ability to process complex information. These deficits can endure for months or even years after the cessation of cannabis use [ref]. Cognitive decline, as measured in loss of IQ points, can in fact be a permanent effect of long-term regular use [ref]. Heavy cannabis use has also been identified as a risk factor for the development of Schizophrenia [ref].

Cannabis is also bad for the lungs and, especially when smoked in rolling papers, can lead to bronchitis, emphysema and lung cancer when used chronically, much like cigarettes.

Long-term use can also lead to Dependence, where users become tolerant to the effects of the drug, require greater and greater doses to achieve similar effects, and experience withdrawal symptoms when they try to cut down.

Cannabis Withdrawal

Stopping cannabis use abruptly after weeks of regular, daily use can lead to restlessness, anxiety, depressed moods, irritability, insomnia, appetite loss, muscle tremors, hyperactive reflexes and changes in heart rate and blood pressure. These effects can last for a few days and up to a couple of weeks. These symptoms are not life-threatening and do not necessitate medical monitoring.

Treating Cannabis Abuse and Dependence

Treating cannabis use disorders follows the general treatment principles as outlined here. There are no medications that have been shown to be effective for this purpose.

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