By Samantha Mellman
BU News Service

(In the recent election, Alaska, Oregon, and Washington, D.C., voted to lift restrictions on marijuana. As the legalization debate continues, we offer this explainer on the question of addiction.)

Every Thursday and Friday night at Harvard’s Divinity School, a small group of people gather to discuss one issue they all believe they share: marijuana addiction.

Marijuana’s Anonymous works the same way as Alcoholics Anonymous. Each person is prompted to work a 12-step program, attend meetings, and eventually live a reefer-free life.

One question that still burns on some people’s minds is: Can marijuana be addictive?

The public wasn’t initially aware that nicotine and cocaine were addictive, and today scientists are still researching the effects of THC, the main psychoactive ingredient in cannbis.

Marijuana policy has become more lenient in the past several years. Following Tuesday’s election, Alaska, Oregon and Washington, D.C,. joined a list of 23 states that allow medical and recreational cannabis.

Addiction is defined as, the state of being enslaved to a habit or practice or to something that is psychologically or physically habit-forming, as narcotics, to such an extent that its cessation causes severe trauma.

Research estimates that nine percent of adults who use it could develop an addiction to marijuana. To put that in perspective, if an estimated 18.9 million people used marijuana in 2012, that means 1.7 million of those people could become addicted.

This percentage doubles in adolescents, because their brains are still in important stages of development, according to research.

When the drug is smoked or ingested, the THC chemical attaches to cannabinoid receptors of nerve cells in the brain. The substance can interfere with many areas of the brain that control emotions, memory, coordination, and sensory and time perception.

Cannabis Use Disorder, the latest term coined in the Diagnostic and Statistical Manual for Mental Disorders, combined two previously separate disorders: Cannabis Abuse and Cannabis Dependence. All these terms are just another way of describing addiction, but opinions vary from doctor to doctor. Marijuana addicts can experience the same obsessions and risk taking behaviors of any drug addicts. Symptoms can range from the drug interfering with a person’s professional or social life to controlling the amount consumed.

A study led by Dr. Jodi Gilman Ph.D., an instructor of psychiatry at Harvard Medical School and a staff member of the Massachusetts General Hospital Center for Addiction Medicine, confirmed that marijuana affects the brain on a biological level. The participants of the study were men and women between the ages of 18-25. They compared brain scans of marijuana users who used at least once a week to non-users.

They focused the nucleus accumbens and amygdala because THC especially affects these parts of the brain that are responsible for pleasure and emotional processing. The study showed that even for non-dependent users these parts of their brains showed abnormalities compared to the control group.

From decades of police seizures of marijuana, scientists discovered that the THC potency has risen from under four percent in 1986 to above 10 percent in 2010. The number of people admitted to treatment centers for marijuana nearly paralleled the increases in THC found in the plants.

Marijuana accounted for 17 percent of all admissions to public abuse treatment programs in 2008. Some doctors speculate that as cannabis becomes more accessible to the general public, the number of people with marijuana addiction may continue to increase.

(Special thanks to: Dr. John Kelly, Ph.D., Associate Professor, Harvard Medical School and Dr. Jodi Gilman, Ph.D., Instructor, Harvard Medical School. Both are on staff at Mass General Hospital’s Center for Addiction Medicine.)

Other Sources:

• http://www.drugabuse.gov/publications/research-reports/marijuana/marijuana-addictive
• http://www.drugabuse.gov/publications/research-reports/marijuana/how-does-marijuana-produce-its-effects
• http://www.massgeneral.org/psychiatry/assets/3Kelly_Med_Marijuana.pdf
• http://addictions.about.com/od/legalissues/a/Cannabis-Use-Disorder.htm
• http://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx
• http://www.jneurosci.org/content/34/16/5529.short?sid=abcc985b-5a29-4f27-893f-df2888594551
• http://www.drugabuse.gov/publications/drugfacts/treatment-statistics
• http://dictionary.reference.com/browse/addiction?s=t -addiction definition