Formation of habitual use drives cannabis addiction

Individual differences in brain systems for habitual behavior distinguish heavy cannabis users who develop an addiction

June 13, 2019

Science Daily/Elsevier

A shift from brain systems controlling reward-driven use to habit-driven use differentiates heavy cannabis users who are addicted to the drug from users who aren't, according to a study in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, published by Elsevier. The findings help explain how the brain becomes dependent on cannabis, and why not all cannabis users develop an addiction, even with long-term regular use.

In the study, researchers at the University of Electronic Science and Technology of China and University of Bonn, Germany, used brain imaging to monitor neural activity when cannabis users viewed images associated with cannabis use, referred to as drug cues. Although all of the cannabis users in the study reported heavy use, only some were dependent on the drug. Both dependent and non-dependent cannabis users had exaggerated responses in a brain region that processes reward -- the ventral striatum -- compared with people who didn't use cannabis. Interestingly, the dependent users also had larger responses in a brain region that forms habits -- the dorsal striatum.

"The present findings reflect that heavy cannabis use is promoted by changes in the brain's reward system -- however, these changes alone may not fully explain addictive use. Addictive use may rather be driven by changes in brain systems that promote habitual -- automatic -- use, which also may explain the fact that addicts continue use despite a lack of experiencing rewarding effects of the drug. As such, their behavior has become under the control of the drug cues, rather than the actual reward expectation," said lead author Benjamin Becker, PhD.

Dependent users also had increased responses in other regions throughout the brain, including regions that attribute importance to things, for example, drug cues. This suggests that the development of cannabis addiction incorporates additional brain regions that may strengthen a person's desire to seek the drug.

"Cannabis is now legal for medical and recreational use in many parts of the United States and the health impacts of this development are still being understood," said Cameron Carter, MD, Editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. "These findings are important insights that can help us better understand why some individuals might be more likely to become addicted to cannabis," he added.

Differentiating the unique brain circuits behind dependent cannabis use could also be useful for understanding how to combat the problem of cannabis addiction. "The identification of the dorsal striatum and habitual behavior as a driver of addiction may allow the development of more specific treatment approaches to increase treatment success," said first author Xinqi Zhou.

https://www.sciencedaily.com/releases/2019/06/190613095213.htm

More than one in ten heavy cannabis users experience withdrawal after quitting cannabis

October 22, 2018

Science Daily/Columbia University's Mailman School of Public Health

As the number of Americans who regularly use cannabis has climbed, so too has the number of those experiencing cannabis withdrawal symptoms. A new study by researchers at the Columbia University Mailman School of Public Health and Columbia University Irving Medical Center finds that 12 percent of frequent marijuana smokers experienced Cannabis Withdrawal Syndrome (CWS), which includes emotional, behavioral and physical symptoms. The study is published in the journal Drug and Alcohol Dependence.

CWS was first included in the Diagnostic and Statistical Manual of Mental Disorders in its most recent edition, DSM-5, published in 2013. The new study is the first large-scale report on the link between CWS and DSM-5 psychiatric disorders among frequent U.S. adult cannabis users.

"In a rapidly changing landscape of marijuana laws and attitudes, cannabis use continues to increase among American adults. As a result, more information on the prevalence and correlates of clinical withdrawal in the general population is of critical importance," said Deborah Hasin, PhD, professor of Epidemiology at Columbia Mailman School of Public Health.

Study participants were interviewed as part of the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III), the only nationally representative survey that measures clinically diagnosed cannabis withdrawal syndrome, which encompasses six psychological symptoms and one or more physical symptoms. Face-to-face interviews in respondents' homes were conducted with 36,309 participants. The final analysis was based on 1,527 participants who were frequent cannabis users, defined as using the drug three or more times a week during the year prior to the interview.

CWS symptoms were associated with numerous psychiatric disorders, significant mental disability, and a family history of depression. Psychiatric disorders included mood disorders; anxiety disorders, including social phobia, agoraphobia, and panic disorder; personality disorders; and post-traumatic stress disorder.

Among withdrawal symptoms, the most commonly reported were nervousness/anxiety (76 percent), hostility (72 percent), sleep difficulty (68 percent) and depressed mood (59 percent). While physical symptoms were reported less frequently than behavioral and emotional symptoms, headaches, shakiness/tremors, and sweating were also prevalent.

Frequent cannabis users were primarily male (66 percent), white (59 percent), aged 18-29 (50 percent), college educated (49 percent), never married (54 percent), and with low household income (45 percent). While frequency of use (within a week) was not significantly associated with withdrawal symptoms, the number of joints smoked per day was significantly associated with withdrawal symptoms.

Cannabis withdrawal syndrome was not significantly associated with family history of drug or alcohol problems, but significantly associated with family history of depression.

"Cannabis withdrawal syndrome is a highly disabling condition," noted Hasin, who is also a professor in the Department of Psychiatry. "The syndrome's shared symptoms with depressive and anxiety disorders call for clinician awareness of cannabis withdrawal symptoms and the factors associated with it to promote more effective treatment among frequent cannabis users."

In an earlier study by Hasin and colleagues (LINK TK), cannabis withdrawal symptoms were prevalent and associated with psychiatric disorders and intensity of cannabis use. However, at that time,NESARC did not cover the DSM-5 cannabis withdrawal symptoms. As a new diagnosis, much remains to be learned about DSM-5 CWS, according to Hasin and colleagues.

"Most users of the newer modes of administration -- vaping and edibles -- also smoke cannabis. Therefore, for users in modes other than smoking, the amount of consumption could be underestimated," said Hasin. "Given the increase in cannabis potency in recent decades, developing reliable measures to investigate the effect of cannabis concentration and mode of administration will be important in advancing our understanding of cannabis withdrawal syndrome."

Co-authors are Ofir Livne (lead author), Lev Hasharon Medical Center, Israel; Dvora Shmulewitz, Columbia University Medical Center; and Shaul Lev-Ran, Lev Hasharon Medical Center and Tel Aviv University.

The study of cannabis withdrawal was supported by the National Institute on Drug Abuse. The NESARC-III survey was supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) with supplemental support by the National Institute on Drug abuse, and by the Intramural Research Program of the NIAAA.

https://www.sciencedaily.com/releases/2018/10/181022122837.htm