Testing Approach Bias for Cannabis Use
The use of cannabis is a hotly debated topic, with some pushing for legalization. While some states allow medical use of cannabis, recreational use is not allowed in the United States. Some proponents of legalizing marijuana insist that its use is harmless and potentially beneficial.
However, many studies have shown that several dangerous effects stem from the use of marijuana. For instance, there is an increased risk of psychosis associated with marijuana use.
There is a great need for full understanding of the use of cannabis and its risk for addiction. A recent study examined whether approach bias related to marijuana-related stimuli could indicate an increased use of cannabis among those who are heavy cannabis users (Cousijn, Goudriaan & Wiers, 2011).
Approach bias is an automatic tendency to be drawn to rather than avoiding drug-related stimuli. It is usually developed after using drugs for an extended period of time.
To test the existence of approach bias, the researchers recruited 32 regular users of cannabis, who were 34 percent female and 41 controls who did not use marijuana (37 percent female). The participants were recruited using Internet ads and advertising through coffee shops located in Amsterdam.
To be eligible for the study, participants had to be a heavy cannabis user or a non-cannabis user. Heavy use was defined as using cannabis on at least 10 of the last 30 days, and using cannabis on at least 240 days over the previous two years.
A non-user met criteria by having used cannabis fewer than 50 times in their lifetime and having no cannabis use over the past year.
The research team utilized an Approach Avoidance Task to test whether the subjects exhibited an approach bias toward marijuana-related cues. The participants were shown cannabis images at a slightly skewed angle, and were asked to use a joystick as quickly as possible to adjust the rotation. A pull on the joystick was considered indicating approach, while a push was an avoidance. Pulling made the image bigger while pushing made it smaller.
The team analyzed approach and avoidance response times for the images, including both cannabis-related and neutral pictures. The participants were also evaluated for cannabis use and related issues. They conducted these analyses both at baseline and six months following the end of the study.
The results of the study indicated that there was a significant increase in cannabis use based on approach bias testing results. It appears that approach bias is a reliable predictor for future cannabis use. The two groups showed no difference in approach bias when responding to neutral images.
The approach bias was not a reliable predictor for changes in dependence or in cannabis-related problems.
The authors of the study note that the small sample size may limit the results when attempting to apply them to a larger population. In addition, many of the participants in the heavy-use group were also tobacco users, which may have affected the approach bias in this group.