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Tokin' concern: Study says marijuana use doubles risk of death, serious injury in car crash

There's a new connection between cannabis and crashes.

Smoking pot before you get behind the wheel makes you twice as likely as your non-toking counterparts to cause a car accident involving a death or serious injury, according to a study in the British Medical Journal. But experts say it's unlikely that this study alone could support an argument for higher auto insurance rates just for marijuana smokers.

For one thing, insurers don’t ask motorists applying for auto insurance about whether they use marijuana, or alcohol for that matter, in assessing their risk. And even if someone is convicted of driving under the influence, insurers generally don't pinpoint whether the driver drank alcohol, smoked marijuana or used other drugs in deciding how much the motorist will pay for coverage.

DUI penalties vary by state. In New York, a first offense results in a driver’s license suspension for at least six months (one year if you're under 21) and up to one year in jail (as many as four years with a passenger under 16). In California, a first offense prompts a four-month license suspension (one year if under 21) with a minimum jail sentence of two days.

marijuana_crash_riskDUI and your auto insurance

While DUI laws differ from state to state, the effect on your auto insurance is pretty consistent across the board. If you're convicted of a DUI for using a substance like alcohol or marijuana, your auto insurance rates likely will shoot up immediately and your insurer may drop you when your policy comes up for renewal, says Michael Barry, a spokesman for the nonprofit Insurance Information Institute.

Auto insurance companies consider all sorts of information, including your location and your driving history, in figuring out how to set rates. To that extent, insurance companies also are interested in research such as the British Medical Journal study, Barry says.

Kris Hermes, a spokesman for the medical marijuana advocacy group Americans for Safe Access, says that auto insurance rates shouldn't be connected to marijuana use and that a single study shouldn't influence insurance companies one way or another.

“If insurance companies want to tie medical marijuana use to insurance rates, certainly there needs to be much more evidence rather than going off this meta-analysis to make that determination," Hermes says. "I would argue that rather than punishing an entire population of people — and this is hundreds of thousands of people across the country — we should use information from accidents to make such determinations on a case-by-case basis.”

The lead author of the British Medical Journal study, Mark Asbridge of Dalhousie University in Nova Scotia, Canada, declines to speculate on whether the study could affect auto insurance rates. But Asbridge and his fellow researchers say the study's findings could be used for campaigns and laws against drug-impaired driving.

The British Medical Journalstudy is a meta-analysis, which crunched the numbers on nine previous studies and scrutinized statistics for nearly 50,000 people. The analysis made no conclusions about how much marijuana you'd have to smoke to push up the risk of a car crash. Studies looked at accidents involving cars, vans, SUVs, trucks, buses, motorcycles and snowmobiles. The study found that the risk of a collision is substantially greater if the driver is under age 35.

The study indicated that the influence of marijuana use on the risk of a minor car crash "remains unclear."

Medical marijuana and traffic deaths

Effects of marijuana on driving are among the aspects of the drug under increasing scrutiny as more states consider the legal use of marijuana by patients with cancer and other medical conditions. So far, 16 states and Washington, D.C., have medical marijuana laws on the books. But results of studies on how pot smoking affects driving have been contradictory.

In contrast to the British Medical Journal study, a 2011 study from the University of Colorado-Denver that analyzed data from 1990 through 2009 found states that have legalized medical marijuana have seen an average 9 percent drop in traffic deaths since their medical marijuana laws took effect.

Authors of the medical marijuana study found that Americans, especially those ages 20 to 29, were switching to marijuana and cutting back on alcohol. The study uncovered evidence that in those states, purchases of beer -- the most popular alcohol choice for young people -- went down and traffic deaths went down, strengthening the already proven connection between alcohol and deadly crashes.

Teen drivers lighting up

Use of marijuana by young drivers is what troubles people at organizations such as SADD (Students Against Destructive Decisions). Nineteen percent of teen drivers report that they'd driven under the influence of marijuana, according to a teen driving study conducted by SADD and Liberty Mutual. That compares with 13 percent of teens surveyed who admit they'd driven after drinking alcohol. In general, marijuana use is on the rise, according to a 2011 study by the University of Michigan and National Institute on Drug Abuse.

Another bit of bad news in the SADD-Liberty Mutual study: 70 percent of teens said marijuana use is “very” or “extremely” distracting for drivers, down from 78 percent in 2009. Stephen Wallace, senior adviser for policy, research and education at SADD, says:"What keeps me up at night is that this data reflects a dangerous trend toward the acceptance of marijuana and other substances compared to our study of teens conducted just two years ago."

Pot vs. booze

Authors of the British Medical Journal study highlighted some of the same results that other research has shown in terms of how marijuana affects the body and mind, according to Paul Armentano, deputy director of NORML, a nonprofit group working to legalize marijuana.

Armentano notes that several studies have indicated that acute marijuana intoxication, which occurs shortly after inhaling it, appears to elevate some people’s accident risk (depending on how much is smoked). That’s why operating a motor vehicle while impaired by marijuana is illegal in all 50 states, he says, and also why NORML’s board adopted a “no driving” provision in its “Principles of Responsible Cannabis Use.”

Armentano points out, however, that marijuana’s effects are rarely severe or long-lasting, unlike alcohol's.

Alcohol’s ties to fatal crashes are well-established. According to estimates from the nonprofit Insurance Institute for Highway Safety, drivers with a blood-alcohol level higher than 0.15 percent (the legal limit in every state is 0.08) are 385 times as likely to be involved in a fatal crash as sober drivers are.

The link between marijuana use and fatal crashes is fuzzy, though. The National Highway Traffic Safety Administration is conducting a study to determine how drug use affects crash risk, spokeswoman Karen Aldana says.

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