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New Research Suggests Daily Marijuana Use Is Not Associated with Brain Abnormalities in Adolescents or Adults


Image credit: Luis Carlos Jimenez del rio

According to some recent researches, smoking marijuana is closely linked with physical changes in certain areas of the brain, as far as shape and volume is concerned. However there is no established cause and effect approved by these studies.

At present, the latest study, by application of a more robust experimental design to replicate such previous investigations, has generated contradictory results. Based on this new research, using marijuana daily, whether by adults or adolescents, is not related with any big differences in terms of both the shape and volume of the regions being investigated. The result of such research work has been released in The Journal of Neuroscience.

Taking the present changing trends concerning the acceptance and use of marijuana into account, it is vital to make a detailed investigation of the probable risks linked with the drug. So any decision in regard to legalization and classification would be made on the basis of scientific evidence. Therefore many studies have focused on the possible effects of using marijuana. As a result, several studies have drawn the conclusion that smoking marijuana is related with changes in the certain areas of the brain. One of the investigations even demonstrated that using marijuana frequently was attributed to cognitive decline as well as IQ decrease. But these results are not always consistent compared with different researches.

For instance, some investigations discovered that using marijuana was associated with a decrease in the size of certain areas of the brain, but others showed that marijuana was linked with an increase in volume of the same areas. Although these researches were quite interesting, it should be admitted that owing to the way they were designed, it would be impossible to establish cause and effect. In addition, these studies might fail to be adequately controlled for alcohol use, which is a very important issue in regard to the well established fact that alcohol abuse could impose a harmful impact on brain structure as well as volume and mental ability.

In order to tackle this issue and offer some clarity if possible, researchers have worked out a well-controlled study targeted on investigation of the potential affects on both adults and adolescents in regard to their marijuana use on a daily basis. More importantly, they were intended to make the comparison between the brains of users and non-users by the means of examining the morphology of numerous different regions which used to be the target the studies carried before, such ad the nucleus accumbens, amygdala, hippocampus and cerebellum.

To implement this research, scientists have enrolled 29 adult daily marijuana users together with 29 adult non-users in addition to the enrollment of 50 adolescent daily users and 50 adolescent non-users. For better result, the scientists were engaged in closely matching the groups in terms of several probable confusing variables, such as age, gender, tobacco use as well as depression. Additionally, they were also matched on alcohol use on a large scale than previous studies.

It was surprisingly noted that MRI scans on the participants and following statistical analyses showed no differences in the volumes of any of the brain regions being investigated. As the research suggested, the previously seen differences could be made because of inadequate control for alcohol use, as it was known that even modest alcohol abuse has been associated with the changes in the brain.

Even if this current study was more robust in regard to matching groups, it should be admitted that some obvious important limitations did exist here, because it fails to  establish causality, nor consider the socioeconomic factors, nor the history of marijuana use, for example, the time when they started to use the drug.

Source: The Journal of Neuroscience

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