Drugs and driving
Implications of drug taking on driving
Illegal drugs
Cannabis is the illegal drug most frequently detected in accident fatalities. Cannabis can impair co-ordination, visual perception, tracking and vigilance. Impairment is also shown when subjects are tested under simulated driving conditions. Despite this, findings relating to the effects of cannabinoids on driving skills and road safety are not conclusive and the consequences of tolerance to cannabis have not been thoroughly explored.
Cannabis may be found in blood as long as 28 days after last use or even longer. Furthermore, it is not known at what level in the blood cannabis causes impairment. Consequently, positive laboratory findings at the time of a motor vehicle crash are only an uncertain indicator that the drug has been used at or near to the time of an accident.
In respect of other drug types, experimental studies suggest that high doses of amphetamines seem to increase risk taking and result in inappropriate and dangerous driving behaviour, such as speeding and carelessness. Studies of cocaine indicate impairment at high doses and during periods of withdrawal.
Recreational drug use and driving: a qualitative study - read more here.
Further information
Department for Transport Local Government and the Regions - read more here
BMA Policy
Therapeutic uses of cannabis (BMA 1997) - read more here
Further reading
US National Library of Medicine - go to the website here
Levy, S. & Jones, A. Improving the debate on cannabis. The effects of cannabis on driving are difficult to evaluate. BMJ 2000;320:1671-2
Seymour, A. & Oliver J.S. Role of drugs and alcohol in impaired drivers and fatally injured drivers in the Strathclyde police region of Scotland, 1995-1998. Forensic Science International 1999;103(2):89-100
Walsh, G. W. & Mann, R. E. On the high road: driving under the influence of cannabis in Ontario. Canadian Journal of Public Health 1999;90(4):260-3
Cooper, F. J. & Logan, B. K. July 2001: GHB (gamma hydroxybutyrate) and driving impairment. Journal of Forensic Science 2001;46(4):919-923.
Payne, HC. Traumatic brain injury, depression and cannabis use – assessing their effects on a cognitive performance. Brain Injury 2000;14(5):479-89
Gouzoulis-Mayfrank, E. et al. Impaired cognitive performance in drug free users of recreational ecstasy (MDMA). Journal of Neurology, Neurosurgery & Psychiatry 2000;68(6):719-25
Holdcroft, A. Adverse effects of cannabis and cannabinoids. British Journal of Anaesthesia 2000;84(3):419-20
Kurzthaler, I. et al. Effect of cannabis on cognitive function and driving ability. Journal of Clinical Psychiatry 1999;60(6):395-9
Parrott, A. C. & Lasky, J. Ecstasy (MDMA) effects upon mood and cognition: before, during and after a Saturday night dance. Psychopharmacologia 1998;139(3):261-8
Hall, W. & Solowij, N. Adverse effects of cannabis. Lancet. 1998;352(9140):1611-6
Prescribed drugs/medicines
The problem of drug driving is not merely related to drug misuse in terms of illegal drugs. The impact of some prescribed drugs (eg sedatives and some anti-depressants) are also relevant. Furthermore, other prescribed treatments such as eye drops can effect vision and hence impair driving ability.
Although patients are warned of the side effects (eg drowsiness), research has shown that they tend to ignore the advice given to them by doctors and pharmacists, and in information leaflets
www.eirpharm.com – read more on the Irish Pharmacy website here). Prescribed drugs can be taken constantly, therefore people may ignore warnings due to the implications on their work and social commitments.
Further information
Royal Pharmaceutical Society - go to the website here
Published an Accident Prevention report in 2000, entitled Medicines that can impair driving.
DTLR
November 2001 'Over the counter medicines and the potential for unwanted sleepiness in drivers: a review
Further reading
US National Library of Medicine - go to the website here
Ridout, F. & Hindmarch, I. Effects of tianeptine and mianserin on car driving skills. Psychopharmacologia 2001;154(4):356-61
Hauri-Bionda, R. et al. Driving fitness/driving capacity of people treated with methadone. Schweizerische Medizinische Wochenschrift 1998;128(41):1538-47
Drugs mixed with alcohol and other conditions
Studies also report that the majority of fatal cases with detected levels of cannabis are confounded by alcohol. Alcohol alone or in combination with cannabis, increases impairment, accident rate and accident responsibility. Therefore, the consequences of mixing alcohol with drugs must also be explored as the side effects of each substance is often exaggerated.
It must also be recognised that other conditions such as fatigue can affect ability to drive, the effects of which will only be compounded by the use of drugs.
Further reading
US National Library of Medicine - go to the website here
Robbe, H. (1998) Marijuana’s impairing effects on driving are moderate when taken alone but severe when combined with alcohol. Human Psychopharmacology: Clinical and experimental 1998;13(S2):S70 – S78
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