Science & Research

Study investigates marijuana dependence

Marijuana-related problems linked to existing impulsivity, memory problems

Contributing Writer
Wednesday, January 30, 2013

Frequent marijuana users tend to perceive their dependency on the drug as less severe than other observers, the study found.

Though only 9 percent of people who have ever used marijuana become dependent on it, frequent usage is often accompanied by problems such as the tendency to procrastinate and a decrease in energy and memory, according to a new study by researchers at the University’s Center for Alcohol and Addiction Studies.

An individual’s likelihood of experiencing marijuana-related problems can be linked to one’s working memory and impulsivity, according to the study, which was  published earlier this month in the journal Drug and Alcohol Dependence.

The researchers employed subjects who were using marijuana about two times per week but who did not experience withdrawal symptoms after refraining from using marijuana for 24 hours, the authors wrote in the study.

To collect baseline data, the study was performed with subjects when they were not under the influence of drugs, said Jane Metrik, assistant professor of behavioral and social sciences.

“If we understand the genetic factors, we can develop medications, take steps to advance the field of marijuana addiction and institute behavioral intervention,” she said.

Using questionnaires and cognitive tests, the study analyzed trait impulsivity, working memory and short-term memory, Metrik said. The results showed users with working memory deficiencies were at increased risk of experiencing marijuana-related problems, but users with short-term memory deficits were not. Frequent users who reported higher impulsivity were also more at risk for problems.

The research was “a solid and focused study that shows that the extent of marijuana-related problems that someone perceives in themselves is a more complex matter than simply how frequently they use,” Nehal Vadhan, a clinical psychology professor at Columbia who was not involved in the study, wrote in an email to The Herald. Vadhan noted in his email that marijuana users may have a biased perception of the effects they experience and suggested a study that would ask people close to each subject for their evaluations of a user’s problems.

Though impulsivity and working memory deficits both correlated with marijuana-related problems, it is unclear if there is a causal relationship between these factors, Metrik said.

As a follow-up to the study, the researchers hope to examine the dual effects of marijuana and alcohol in frequent marijuana users.

The study was part of a larger research project through the center examining genetic makeup and cannabis dependence. The larger project is funded by the National Institute on Drug Abuse and was led by Metrik, Associate Professor of Psychiatry Valerie Knopik, Associate Professor of Psychiatry and Human Behavior John McGeary, Professor of Behavioral and Social Sciences Christopher Kahler and Professor of Behavioral and Social Sciences Damaris Rohsenow. The study’s lead author was post-doctoral fellow Anne Day.

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  1. Scientific fact: Marijuana is less addictive than a cup of tea.

    Dr. Jack E. Henningfield of the National Institute on Drug Abuse and Dr. Neal L. Benowitz of the University of California at San Francisco ranked six psychoactive substances on five criteria.

    Intoxication — The degree of intoxication produced by the drug in typical use.

    The tables listed below show the rankings given for each of the drugs. Overall, their evaluations for the drugs are very consistent. It is notable that marijuana ranks below caffeine in most addictive criteria, while alcohol and tobacco are near the top of the scale in many areas.

    The rating scale is from 1 to 6 — 1 denotes the drug with the strongest addictive tendencies, while 6 denotes the drug with the least addictive tendencies.


    Withdrawal Reinforcement Tolerance Dependence Intoxication

    Nicotine 3 4 2 1 5

    Heroin 2 2 1 2 2

    Cocaine 4 1 4 3 3

    Alcohol 1 3 3 4 1

    Caffeine 5 6 5 5 6

    Marijuana 6 5 6 6 4


    Withdrawal Reinforcement Tolerance Dependence Intoxication

    Nicotine 3 4 4 1 6

    Heroin 2 2 2 2 2

    Cocaine 3 1 1 3 3

    Alcohol 1 3 4 4 1

    Caffeine 4 5 3 5 5

    Marijuana 5 6 5 6 4

  2. couldn’t this data also imply that marijuana helps increase working memory capacity, therefore people with a deficiencies in that department tend to use it. In which case is it not possible that it has the same effect on normal people and enhances their working memory to beyond normal? cuz that’s how it feels like

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