Pot-Smokers, Schizophrenics Show Similar Brain Changes

The potential association between marijuana and mental health conditions is one of the most commonly stated negative effects of the drug, but the picture is far from a clear one. However, a new piece of research has investigated the association between marijuana use, working memory and variations in brain structure in both schizophrenic participants and healthy ones. The findings reveal that pot-smokers have similar neurological changes to schizophrenics and perform much worse than non-using participants on memory tasks. What this means for the link between marijuana and mental health problems is still ultimately unclear.

The Study

The research involved about 100 teens aged 16 and 17, both ex marijuana-smokers and never-users, with both schizophrenics and healthy subjects included. They study authors split the teens into four groups based on past marijuana use (the ex-users had smoked the drug every day for at least three years in the past) and whether they did or did not suffer from schizophrenia. The complete sample consisted of 44 never-smoking healthy controls, 10 of which had a history of marijuana use but no schizophrenia, 28 never-smoking schizophrenics and 15 sufferers who had used marijuana in the past. Importantly, the participants hadn’t consumed any drug other than marijuana.

MRI machines were used to map the structure of specific brain regions, and the participants were also given tests to determine what effect—if any—past marijuana usage had on working memory in both schizophrenics and non-schizophrenics. The research was cross-sectional, however, meaning that it was only sufficient to establish an association between marijuana use and the outcome measures, not a definite cause-and-effect relationship.

What They Found

The study’s results showed that past marijuana use was associated with shrinking in areas of the brain related to working memory, regardless of whether the participant suffered from schizophrenia. This may seem incidental and of little relevance, but poor working memory is associated with difficulties in everyday functioning and in academic settings. Additionally, the researchers found issues with the thalamus of marijuana-users, which is an important area of the brain for things like communication, learning and memory.

The neurological changes were also demonstrated to have a real-world impact through the use of a memory test. The healthy participants who had regularly consumed marijuana in the past scored 37 times worse on the test than those who hadn’t consumed the drug, and the schizophrenia-suffers who consumed marijuana did four times worse than those who didn’t. Since the participants had all already stopped consuming marijuana, this could suggest a long-term impact on the brain from regular pot smoking.

The brain changes observed in marijuana users (which were more pronounced in the schizophrenia-suffering users) were similar to those observed in schizophrenics in general, as one of the researchers, Dr. John Csernansky, pointed out, “This paper is among the first to reveal that the use of marijuana may contribute to the changes in brain structure that have been associated with having schizophrenia.”

Contrary Findings

The complete picture of the research on the link between marijuana and schizophrenia isn’t quite so clear-cut, however. The most basic observation to cast some doubt on the link is the stable incidence of schizophrenia over time, despite the vast increase in marijuana use following the 1960s. The often-observed correlation between marijuana and schizophrenia (or earlier onset of schizophrenia) may be related to gender differences, because men are more likely to smoke marijuana heavily and generally develop schizophrenia earlier. Other research has also suggested that a smaller subgroup of schizophrenia sufferers is more likely to have negative consequences following marijuana use. There are many potential explanations for this, but the leading theories are that a family history of schizophrenia and earlier onset of use of marijuana are associated with this susceptibility.

Of course, research has uncovered links between marijuana use and schizophrenia many times in the past, but none has been conclusive in either direction. The recent study, for example, provides interesting new information but isn’t longitudinal, so it only reveals a correlation between the brain changes, working memory issues and marijuana use. In other words, it could be that smoking marijuana impacts your brain, destroys your working memory and makes schizophrenia more likely, or it could be that those with poor memories or who suffer from schizophrenia or who have neurological differences are more likely to consume marijuana. The uncertainty comes from the fact that you can’t call the issue one way or another without doing several ethically questionable clinical trials where groups of participants are randomly-assigned to either regular marijuana use or complete abstinence and their outcomes carefully measured.

Additionally, although the primary psychoactive component of marijuana, THC, does appear to create psychological issues, the other component, CBD, actually appears to treat psychological issues. It makes sense from a chemical perspective that we would find contrary results when it comes to the mental health impacts of marijuana.

The Chicken or the Egg?

At the moment, we’re left guessing: It could be that marijuana use comes first and problems follow, or that problems come first and marijuana use follows. However, what we do know is that heavy marijuana use, like any heavy drug use, is probably a flawed coping mechanism for dealing with other issues. In other words, even if we can’t currently say that heavy marijuana use leads to schizophrenia or working memory problems, there are still numerous reasons to abstain from or at least minimize marijuana use.

Posted on January 30th, 2014
Posted in Abused Drugs

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