Marijuana, derived from the hemp plant Cannabis sativa, is used as both a recreational drug and a medicinal treatment, though it is not approved as such by the U.S. Food and Drug Administration. It is the most commonly used illicit drug in the United States, according to the National Institute on Drug Abuse. Contrary to popular belief, marijuana can be psychologically and physically additive, with withdrawal symptoms that can hinder cessation.
Effect of Marijuana on the Brain
The main active ingredient in marijuana is delta-9-tetrahydrocannabinol, or THC. THC resembles a chemical called anandamide, which exists naturally in the brain and binds to cannabinoid receptors, according to the National Institute on Drug Abuse. This neural communication network, called the endocannabinoid system, plays an important role in normal brain development and function. THC's similar structure allows it to be recognized by these receptors and to alter normal brain communication. This creates the "high" sensation, which may include altered perception or mood, impaired coordination, difficulty with thinking and disrupted learning and memory.
Tolerance to Marijuana
Tolerance describes an adaptation by the body to a drug that requires higher doses to obtain the effect of the initial dose. It is thought that tolerance contributes to the development of dependencies and that withdrawal symptoms reflect the inability to function without the accustomed drug. Chronic or daily use of marijuana will likely result in tolerance, says the National Drug Institute, although there is no specific time frame or dose of marijuana that dictates when tolerance begins to occur.
Cannabis Use Disorder
Although marijuana is not as addictive as many other illicit drugs, 9 percent of individuals who have ever used cannabis develop a dependence, according to a 2007 analysis published in "Addiction Science and Clinical Practice." Since the prevalence of use is so high, this results in more than twice as many Americans with marijuana dependency versus dependency on any other drug, including cocaine and heroin. Children, young adults and daily users are at the greatest risk of developing a dependency, with individuals younger than 25 accounting for approximately half of all patients seeking treatment for cannabis use disorder.
Cannabis Withdrawal Syndrome
The American Psychiatric Association says that cannabis withdrawal syndrome is experienced by up to 50 percent of patients treated for both psychological and physiological marijuana dependency. Neurobiological withdrawal from marijuana has been linked to the cannabinoid receptors in the central nervous system, as suggested by a 2012 analysis by the Psychiatric Clinics of North America. Onset generally occurs during the first week of abstinence and can last for several weeks. Symptoms may include a dysphoric mood -- such as anxiety, irritability, restlessness or depression -- disturbed sleep and decreased appetite or other gastrointestinal symptoms. To date, no approved drugs have been developed to help treat cannabis withdrawal syndrome, although psychotherapy methods such as motivational enhancement therapy may be helpful.
- National Institute on Drug Abuse: Marijuana
- American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, 5th ed.
- Addiction Science and Clinical Practice: Marijuana Dependence and Its Treatment
- Psychiatric Clinics of North America: State of the Art Treatments for Cannabis Dependence; 2012