Smoking cannabis “warps the brain and shrinks grey matter” – study

smoking marijuana and drinking beer amid clouds of smokeTEXAS, United States, Wednesday November 12, 2014 – While the decriminalisation of marijuana continues to be a hot topic in the Caribbean, the findings of a new American study have lent weight to a growing body of evidence that suggests cannabis is more harmful than legalisation campaigners would have us believe.

According to scientists at the universities of Texas and New Mexico, regular use of the drug appears to warp key structures of the brain, shrinking the “grey matter” – the cells that crunch information.

And while the wiring of the brain (the “white matter” that connects different areas) grows to compensate for the loss, scientists found that also eventually breaks down, impairing the ability to use and react to information.

The findings of the new study led its authors to warn that people who take the drug in heavy quantities for prolonged periods are likely to suffer damaging effects.

The scientists studied magnetic resonance imaging (MRI) scans of the brains of 48 adult cannabis users aged 20 to 36 who were compared with a group of 62 non-users.

On examining the scans, the researchers found that chronic marijuana users (those who smoked an average of three times a day) had smaller average volumes of grey matter in the orbitofrontal cortex, the part of the brain involved in mental processing and decision making.

The orbitofrontal cortex region of the brain is also strongly linked to the ability to relate to the feelings of others.

Neuroscientists believe damage to the orbitofrontal cortex may underpin many cases of personality disorder and psychopathy.

The team from the universities of Texas and New Mexico found that the effect differed markedly depending on the age persons started smoking cannabis and the number of years they continued to use the drug.

The earlier they started, the greater the structural change to the brain and the larger the growth in white matter connections, the scientists found.

But even those extra connections were seen to break up within six to eight years under prolonged cannabis abuse, they found.

The brain scan study is one of the first to investigate the drug’s long-term neurological impact in living human beings.

According to the University of Texas’ Dr Sina Aslan: “What’s unique about this work is that it combines three different magnetic resonance imaging techniques to evaluate different brain characteristics.

“The results suggest increases in connectivity, both structural and functional that may be compensating for grey matter losses.

“Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use.”

The scientists said that while the statistical picture they built up suggests that the drug abuse is linked to the structure of the brain, more research is needed to be absolutely sure.

The study’s co-author Dr Francesca Filbey, also from the University of Texas, said: “We have seen a steady increase in the incidence of marijuana use since 2007.

“However, research on its long-term effects remains scarce – despite the changes in legislation surrounding marijuana and the continuing conversation surrounding this relevant public health topic.

“While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use.”

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