The prevalence of cannabis-involved driving in California

Abstract

Background Various national surveys suggest that cannabis use is rising nationally, and many States have passed legislation that has potential to increase usage even further. This presents a problem for public roadways, as research suggests that cannabis impairs driving ability. Methods Anonymous oral fluid samples and breath tests were obtained from more than 900 weekend nighttime drivers randomly sampled from six jurisdictions in California. Oral fluid samples were assayed for the presence of Schedule I drugs. Drivers also completed information on self-reported drug use and possession of a medical cannabis permit. Data from the 2007 National Roadside Survey (collected using comparable methods) were used as a comparison. Results Using the 2010 data, a total of 14.4% of weekend nighttime drivers tested positive for illegal drugs, with 8.5% testing positive for delta-9-tetrahydrocannabinol (THC). THC-positive rates varied considerably among jurisdictions, from a low of 4.3% in Fresno to a high of 18.3% in Eureka. A comparison with the 2007 NRS data found an increase in THC-positive drivers in 2010, but no increase in illegal drugs other than cannabis. Drivers who reported having a medical cannabis permit were significantly more likely to test positive for THC. Conclusions Cannabis-involved driving has increased in California since 2007. Nearly 1-in-10 weekend, nighttime drivers tested positive for THC, and in some jurisdictions, the rate was nearly 1-in-5. The possible contribution of cannabis legislation, such as decriminalization and medical cannabis usage, is discussed.

Drugged Driving: Increased Traffic Risks Involving Licit and Illicit Substances

“…Marijuana has been decriminalized in the District of Columbia and 20 states including Washington, Oregon, California, Nevada, Montana, Colorado, (Cerda, Wall, Keyes, Galea, & Hasin, 2012;Office of National Drug Control Policy, n.d.). Indications are that changes in marijuana policy reflect community opinion, thus marking changes in social standards about marijuana use and access to marijuana (Cerda et al, 2012;Johnson et al, 2012). Yet, results of this study underscore that cannabis users in particular, compared to users of other substances, engage in dangerous driving behaviors as indicated by the higher number of traffic citations, thus placing themselves and other drivers at risk.…”

“…The most prevalent drugs of abuse are cocaine, opiates, amphetamine/ methamphetamine, cannabis, and benzodiazepines (Lacey, Kelly-Baker, FurrHolden, Boas, Romano, Torres, et al, 2009). After alcohol, cannabis was the most frequently used substance in the majority of impaired driving studies (Johnson, Kelley-Baker, Voas, & Lacey, 2012;Longo, Hunter, Lokan, White, & White, 2000;Sewell, Poling, & Sofuoglu, 2009). In combination with alcohol, cannabis produces acute impairment in defensive driving strategies, such as a slower rate of driving speed (Hartman & Huestis, 2013;Sewell et al, 2009).…”

Risk Factors for Driving After and During Marijuana Use

“…Crash risk increases progressively with the dose and frequency of marijuana use (Li et al, 2012), with the risk of being involved in an accident virtually doubling after marijuana use (Ramaekers et al, 2004). This dose-dependent association is particularly alarming because of the increasing potency of marijuana (Mehmedic et al, 2010;Vindenes et al, 2013) and the increased prevalence of marijuana-involved driving in recent years (Johnson et al, 2012). Furthermore, acute marijuana use has been associated with reported reduction in driving speed; however, such conscious efforts to compensate for potential impairment may be misleading as they are largely unsuccessful and likely contribute to a false perception of safer driving (Bates & Blakely, 1999).…”

Police custody following driving under the influence of cannabis: A prospective study

“…Detention for cannabis-involved driving or for possession of cannabis is misinterpreted by arrestees, who commonly do not consider it as a complication of substance use. Cannabis users do not perceive cannabis use as being associated with increased driving risk [32,33]. Medical care in custody of detainees arrested in relation to substance misuse could include brief interventions on addictive behaviours [34].…”