Re: Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis
Cannabis use is common (1) and according to the recent metanalysis by Ashbridge, et al (2) is a risk factor for road traffic accidents. Cannabis is often consumed in the evening, and it is known that accidents are more frequent between the hours of 2 – 7am (3,4). This increased frequency of accidents has been considered to be due to the cumulative effects of sleep deprivation and the trough of performance related to the circadian system, as the reduction in performance after 17 hours of wakefulness is equivalent to that seen in subjects with a blood alcohol level of 0,05% (5). However undiagnosed drug use may also contribute.
Ashbridge et al point out that confounders were not controlled for in many of the studies they included in their metanalysis. We suggest that sleep deprivation and circadian rhythm phase may interact with the effects of cannabis, creating a greatly increased risk of accident. Further research should include the time of consumption, sleep habits and the time of accidents in order to better understand the contributions of different risk factors.
1. Degenhardt L, Chiu WT, Sampson N, et al .Toward a global view of alcohol, tobacco, cannabis, and cocaine use: findings from the WHO World Mental Health Surveys. PLoS Med. 2008 Jul 1;5(7):e141.
2. Asbridge M, Hayden JA, Cartwright JL Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis. BMJ. 2012 Feb 9;344:e536. doi: 10.1136/bmj.e536.
3. Horne JA, Reyner LA Sleep related vehicle accidents. BMJ. 1995 Mar 4;310:565-7.
4. Garbarino S, Nobili L, Beelke M, De Carli F, Ferrillo F.The contributing role of sleepiness in highway vehicle accidents. Sleep. 2001 Mar 15;24(2):203-6.
5. Dawson D, Reid K. Fatigue, alcohol and performance impairment. Nature 1997;388: 235.
Competing interests:
No competing interests
28 February 2012
Sarah Hartley
Sleep Physician
Maria-Antonia Quera-Salva
Hôpital Raymond Poincaré
104 Boulevard Raymond Poincaré, 92380 Garches, FRANCE
Rapid Response:
Re: Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis
Cannabis use is common (1) and according to the recent metanalysis by Ashbridge, et al (2) is a risk factor for road traffic accidents. Cannabis is often consumed in the evening, and it is known that accidents are more frequent between the hours of 2 – 7am (3,4). This increased frequency of accidents has been considered to be due to the cumulative effects of sleep deprivation and the trough of performance related to the circadian system, as the reduction in performance after 17 hours of wakefulness is equivalent to that seen in subjects with a blood alcohol level of 0,05% (5). However undiagnosed drug use may also contribute.
Ashbridge et al point out that confounders were not controlled for in many of the studies they included in their metanalysis. We suggest that sleep deprivation and circadian rhythm phase may interact with the effects of cannabis, creating a greatly increased risk of accident. Further research should include the time of consumption, sleep habits and the time of accidents in order to better understand the contributions of different risk factors.
1. Degenhardt L, Chiu WT, Sampson N, et al .Toward a global view of alcohol, tobacco, cannabis, and cocaine use: findings from the WHO World Mental Health Surveys. PLoS Med. 2008 Jul 1;5(7):e141.
2. Asbridge M, Hayden JA, Cartwright JL Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis. BMJ. 2012 Feb 9;344:e536. doi: 10.1136/bmj.e536.
3. Horne JA, Reyner LA Sleep related vehicle accidents. BMJ. 1995 Mar 4;310:565-7.
4. Garbarino S, Nobili L, Beelke M, De Carli F, Ferrillo F.The contributing role of sleepiness in highway vehicle accidents. Sleep. 2001 Mar 15;24(2):203-6.
5. Dawson D, Reid K. Fatigue, alcohol and performance impairment. Nature 1997;388: 235.
Competing interests: No competing interests