SEVERAL research studies are currently being done on ganja in academic institutions across Jamaica, especially since the decriminalising of possession of less than two ounces of ganja.

However, research in other jurisdictions is also being done — some with findings that confirm that ganja may do harm in some ways, even if beneficial in other ways.

One research finding published in the Journal of the American Medical Association Internal Medicine recently was that marijuana or ganja may impair verbal memory, which is the ability to remember certain words and other abstractions involving language.

It has long been stated that ganja may harm the brain, particularly in children and teenagers when brain development is proceeding rapidly, and that ganja use was linked to memory dysfunction. Now the researchers from the Department of Ambulatory Care and Community Medicine at the University of Lausanne, Switzerland, found that individuals with long-term exposure to ganja may experience significant impairment of verbal memory by the time they reach middle age, but that other aspects of cognitive function, which are activities of the brain that lead to knowledge, were not affected.

WORSENED VERBAL MEMORY AND PROCESSING SPEED

The researchers reported that for each additional five years of exposure to marijuana, there was a significant decline in performance of people on a standard verbal memory test.

They recommended future studies with multiple assessments of cognition, brain imaging, and other functional outcomes to further explore these associations and their potential implications for clinical and public health. Also, they recommended that with the recent changes in legislation occurring in some jurisdictions and the potential for the increased use of marijuana, it is more than reasonable to warn potential users about the possible harm from exposure to marijuana.

To conduct the research, the researchers examined data from 5,115 black and white men and women from four sites in the United States of America, who were recruited in 1985 and followed through until 2011. The lifetime use of marijuana was assessed in 1985, and again after two, five, seven, 10, 15, 20, and 25 years of follow-up.

Cognitive (mental) function was assessed at the 25-year follow-up using the Auditory Verbal Learning Test and the Digit Symbol Substitution Test. The researchers found that current marijuana use was associated with worse processing speed and verbal memory on the tests.

With this association strongly confirmed, the researchers posited possible explanations for the association between long-term marijuana use and worse verbal memory. They stated that marijuana has been associated with underlying measures that are linked in the hippocampus section of the brain. Structural changes in the hippocampus could explain the associations, whereby people would have a problem retaining words, but this would not impact on other domains of brain cognition.

WELCOMED ADDITIONAL RESEARCH

This research finding has been welcomed in academic institutions in other countries as adding significantly to the research literature, as it is rare to have longitudinal studies that involve the use of marijuana, and this investigation confirmed previous associations between the use of marijuana and poorer cognitive function.

The participants in the study were middle-aged, due to the 25-year period of the research. The impairment of memory function was not age-related, but rather due to the cumulative exposure to marijuana, thereby indicating that greater use of marijuana at any age has the potential to impair cognitive functioning.

The research study specifically indicated that, on average, one in every two people will recall one word less from a list of 15 words for every five years of marijuana use. This indicates a gradual and subtle loss of memory function which will have a greater impact on daily functioning the longer the marijuana is used. This potential interaction with brain development at critical ages, and in individuals already compromised by neurological, psychiatric, socio-economic, and other factors, therefore warrant public health concerns regarding the use of ganja in the community and in the wider society.

AVOID SMOKING

Further research is necessary to discover whether any of the memory dysfunction that is associated with ganja use can be reversed following prolonged abstinence from ganja. However, for now we must disseminate the word that all young people should avoid smoking ganja and avoid inhaling its smoke when it is being smoked around them.

Alongside our efforts not to make criminals of those who smoke ganja, we must emphasise to all persons that smoking prevents them from achieving their maximum cognitive (mental) output. As ganja smoking can occur in private homes, dwellings, or premises out of sight of the public (and of the police where youngsters are concerned), public enlightenment and increased awareness of these issues with the requisite action should help to reduce the risk of a greatly under-achieving populace in the years to come.

Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the Ethicist at the Caribbean Public Health Agency – CARPHA. (The views expressed here are not written on behalf of CARPHA).