On June 5, The New England Journal of Medicine published a comprehensive review of cannabis, more commonly referred to as marijuana, and the consequences of its long-term use. The group reported that marijuana use is associated with substantial adverse effects, and some effects have been determined with a high level of confidence.

Regular and heavy recreational use of cannabis has been strongly linked with addictive behaviors and motor vehicle accidents. Unfortunately, law enforcement officers in the United States don't have a reliable means of testing for drug impairment. But that may be changing soon with new research and legislation.

Colorado looked at data prior to the legalization of marijuana — data during the the period of legalization for medical use, but prior to full legalization — and found an alarming increase in the rate of fatal motor vehicle crashes.

When analyzing the National Highway Traffic Safety Administration Fatality Analysis reporting system from 1994-2011, University of Colorado School of Medicine researchers compared fatal motor vehicle crashes in Colorado to 34 states that did not have medical marijuana laws. They found that the proportion of drivers who were marijuana-positive had dramatically and significantly increased.

The increased use of marijuana with legalization for recreational use in two states and for medicinal use in 22 other states is creating alarm for law enforcement agencies. There are limits on the ability for law officers to test for impairment to drive.

Many countries currently use saliva swabs to determine the presence of marijuana in drivers. The state of Michigan was the first U.S. state to put forth such testing as part of a bill in the legislature intended to increase police officers' ability to better identify repeat drug-impaired drivers.

The bill had a section proposing that police agencies could obtain saliva samples as a means to objectively quantify probable impairment to drive due to drug use. However, the section regarding the saliva testing was later removed.

The lack of such a test is of concern to law enforcement agencies across the country.

"If you look at our crime stats, compared to five years ago, we have a whole lot more (arrests for) drugged driving — it's a change of culture going on," police Sgt. Andy Breidenich in Troy, Michigan, told the Detroit Free Press. "While officers can use a portable breath tester to establish a basis for arrest of a suspected drunken driver, they have no such physiological test for drugged drivers.

"So officers put motorists suspected of abusing drugs through field sobriety testing, which includes an officer's visual exam of the suspect as well as the administration of a battery of simple verbal and physical tests."

Numerous countries already use saliva as a field test to detect drugs — including marijuana — in impaired drivers. Australia has laws that allow for random roadside testing, and drivers stopped by police may be required to provide a saliva sample. The intent is not to quantify any level of impairment, but to simply identify the presence of drugs.

The United Kingdom and Wales are using saliva collection in 11 police districts. In France, drivers suspected of drug use are required to spit on a test stick. If the test determines the presence of drugs, the positive result is followed up by a blood test.

A similar strategy is used by police in Switzerland, but the Swiss officers can use either saliva or urine for the initial screen to detect cocaine, heroin, marijuana or amphetamines. If that test is positive, the suspect is taken to the hospital for blood testing.

Mothers Against Drunk Drivers (MADD) is strongly advocating for laws allowing for saliva testing in Canada. Jan Withers, the U.S. national president of MADD, expressed concern about reports of increased fatalities attributed to impaired driving while under the influence of marijuana.

"MADD is concerned anytime we hear about an increase in impaired driving, since it's 100 percent preventable," Withers told HealthDay News. "When it comes to drugged driving versus drunk driving, the substances may be different but the consequences are the same — needless deaths and injuries."

While the use of a breathalyzer test for alcohol is a standard procedure for law enforcement, no such tool exists for recreational or medicinal drugs than can cause impairment to drive. The use of tests for saliva, currently used throughout Europe and in Australia, are met with significant resistance within the United States with concerns about accuracy and the detection of residual cannabis in the system in habitual users.

Yet there remain active lines of research that are demonstrating the increasing accuracy and sensitivity of saliva tests for marijuana. An accurate and reliable "spitalyzer" may soon be in the arsenal of law enforcement officers to use in the fight against impaired driving.