As we discuss decriminalising ganja use in Jamaica, in addition to keeping children and adolescents away from the drug, we must also discuss how we can reduce any effect ganja use may be contributing to motor vehicle accidents across our land.

Research has shown, and the Report of the Ganja Commission has detailed how ganja impairs psychomotor and cognitive function and may therefore affect the driving of a motor vehicle or operating machinery.

A study by Carl Stone in 1990 among persons over the age of 15 years revealed that 47 per cent of persons in the metropolitan area and 43 per cent in the rural areas of Jamaica had used ganja. Its usage cut across all social, educational, and economic groups.

While no similar research has been done in Jamaica, results from a 2009 Canadian Alcohol and Drug Use Survey indicated that the rates of driving under the influence of marijuana had risen over the years, with their national data in 2004 indicating that four per cent of Canadian adults reported driving within one hour of consuming marijuana, up from 1.9 per cent recorded in 1996-7.

These results are reflected in other jurisdictions across the world. A roadside survey of 537 drivers in Scotland reported that 15 per cent of respondents aged 17-39 years admitted to having taken or used marijuana within 12 hours of driving a vehicle, and the European Monitoring Centre for Drugs and Drug Addiction found that between 0.3 per cent and 7.4 per cent of drivers tested positive for marijuana from roadside surveys in the United Kingdom, Denmark, The Netherlands, Norway, the United States, and Australia.

The effects of ganja on driving

Much of the early research assessing the effects of marijuana on driving performance was done by laboratory and driving simulator studies. The results of these studies were generally consistent: at increased doses, marijuana impairs the psychomotor skills necessary for safe driving. Many subsequent studies have reported on the incidence of marijuana in injured or fatally injured drivers, as well as in the general driving public.

A meta-analysis of these studies, published in the British Medical Journal in 2012, revealed that marijuana was consistently one of the most frequently detected psychoactive substances (second after alcohol), and individuals who drive

within two hours

of using marijuana have raised rates of collision.

The meta-analysis included observational studies of motor vehicle drivers who had been treated for serious injuries sustained in a crash or had been involved in a fatal crash. All studies tested for tetrahydrocannabinol (THC) by analysing blood samples or using direct self-reports of marijuana use in the three hours before the crash.

The studies were undertaken in different countries, and the rates of marijuana use for cases ranged from two per cent to 15 per cent. The results showed that acute marijuana use nearly doubles the risk of a collision, resulting in serious injury or death.

Motor vehicle accidents in Jamaica

How might the use of ganja before driving be affecting the prevalence of traffic accidents here? Last year, our road fatalities increased by 17 per cent above the previous year.

In 1999, McDonald and other researchers took blood and urine samples for testing from 111 trauma patients seen at the Accident & Emergency Department of the University Hospital of the West Indies over a three-month period, and results showed 25 per cent of these persons tested positive for ganja, 15 per cent tested positive for both ganja and alcohol, 15 per cent for alcohol only, and five per cent tested positive for both ganja and cocaine.

Whilst our police officers sometimes do breathalyser tests for alcohol use in drivers, we do not test for any ganja present in those drivers or in offending pedestrians in Jamaica. Yet research has confirmed that ganja use impairs judgement, and this is relevant for pedestrians, pedal cyclists, as well as drivers.

Excessive speeding, improper overtaking, tail-gating, headlight glare, stopping without warning or at improper locations, and other forms of dangerous driving may all be due to such impairment of judgement. The acute intake of substances like alcohol or ganja that reduce one’s reaction (reflexes) and cognitive function (judgement) therefore may be playing a significant part in the accidents on our roads.

The National Road Safety Council has been emphasising the need for Jamaicans to pay closer attention to the high incidence of motor vehicle accidents, and to speak out against speeding drivers, those driving under the influence of alcohol or distracted by cellphones or music. Informed by these results from research, we must now add ‘those driving under the influence of ganja’ to this list.

The information regarding ganja’s effects on judgement and reflexes, plus the doubling of the risk for serious accidents when driving under the influence of ganja, should be used to raise public awareness and form the basis for campaigns against drug-impaired driving. It should also be used in developing national policies and interventions to control acute drug use while driving. We should all be concerned about public health.

— Dr Derrick Aarons MD, PhD is a consultant bioethicist/family physician, specialist in ethical issues in medicine, the life sciences and research, and is a member of the Executive Council of RedBioetica UNESCO.