How Marijuana Alters Decision-Making

Decision-making is the logic-based thought process that humans use to analyze any given situation and determine how to respond to that situation going forward.

Scientific evidence suggests that disruptions in the normal use of this process contribute substantially to increased risks for developing a problem with drug or alcohol intake.

In a 2013 Addiction Biology study,  researchers from the Netherlands and the U.S. assessed the ways in which changes in the brain’s decision-making process can boost a cannabis user’s chances of increasing his or her level of drug consumption over time.

Cannabis/marijuana use

Cannabis (marijuana, hashish and hashish oil) is a popular recreational drug also noted for its potential usefulness in certain limited medical circumstances. Roughly 2.5% of the world’s population uses some form of the drug at one time or another. In America, use of marijuana is fairly common among a range of age groups.

Harms of marijuana

Whether consumed in a recreational or medicinal context, cannabis has a known potential to produce a range of significant harms, including such things as serious, non-addicted cannabis abuse and cannabis addiction (known together as cannabis use disorder), a long-term reduction in the ability to think clearly or understand multi-layered information, increased risks for bronchitis or other damaging respiratory ailments, an increased susceptibility to infections that enter the body through the lungs, a short-term disruption of muscle coordination and awareness that can contribute to accidental injury, increased risks for the onset of psychosis-like symptoms and the worsening of existing symptoms of psychosis.

Decision-making fundamentals

As a rule, decision-making involves a multi-part process. Specific steps in this process include such things as:

  • Recognizing the need for action
  • Acquiring information to fuel the problem-solving
  • Identifying the potential choices
  • Calculating the pros and cons
  • Selecting a plan of attack
  • Acting, and then reflecting on the outcome later

The capacity to make decisions belongs to a group of higher-level thought processes that experts in the field refer to by the collective term “executive function.” Like all human mental capabilities, it relies on the brain’s ability to properly perform its basic tasks.

Marijuana’s impact on decision-making

In the study published in Addiction Biology, researchers from the University of Amsterdam, Wake Forest University and the Netherlands’ Arkin Mental Health used a brain imaging technique called fMRI (functional magnetic resonance imaging) scanning to examine the moment-to-moment functioning of the brains of 32 people with an ongoing history of heavy marijuana intake, as well as the moment-to-moment functioning of the brains of a comparison group of 41 people not involved in cannabis use.

Brain imaging was conducted while all of these individuals were taking part in a common decision-making test called the Iowa Gambling Task, which asks users to make win-or-lose choices while playing a card game with a monetary reward. The researchers used the information gathered from fMRI scanning and the Iowa Gambling Task to compare the decision-making processes of heavy cannabis users to the decision-making processes of people who don’t consume cannabis. They also used the same information to determine how the decision-making processes of heavy cannabis users change over a six-month period of time.

After completing their comparisons, the researchers came to several conclusions. First they found that heavy cannabis users perform roughly as well on the Iowa Gambling Task as people who don’t consume cannabis. However, in order to achieve this comparable result, these individuals must use more of their brains’ overall work capacity. The researchers also found that, among people heavily involved in marijuana intake, some people have brain-based problems with normal decision-making that increase their chances of consuming more and more of the drug and potentially triggering serious cannabis-related health problems.

New marijuana research discovery

These findings were in line with the expectations created by previous research on the decision-making powers of heavy cannabis users. However, the researchers also made a new discovery: Cannabis users who show a strong bias toward accepting short-term rewards have a significantly higher chance of increasing their intake of the drug over time than cannabis users who engage more thoroughly in the decision-making process and delay their personal gratification until a later date. The authors of the study point to this new result as an indication of the fairly delicate equilibrium that exists between brain-based habits that support the onset of substance abuse and brain-based habits that help prevent substance abuse.

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