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OK, so marijuana is now legal in Washington state. But does that mean it's good for you?

"Dailyuse increases the risk of becoming dependent," says Roger Roffman, aprofessor emeritus at the University of Washington's School of SocialWork. He supported Initiative 502, which called for the legalization of asmall amount of marijuana for adults 21 and older in Washington.

Roffmansays there are positive effects of marijuana use: It can help peoplerelax and interact with others. It also can enhance some sensoryexperiences, such as listening to music. And consumption for medicalpurposes can reduce symptoms of disease and treatments of disease, hesays.

But dependence can cause impairment or distress and othereffects that interfere with other areas of life, he says. "It's fairlycommon for people who are using marijuana regularly to complain thattheir ability to think clearly is impaired - to remember, to organizetheir thoughts, to follow through with multitasking."

THC, theactive ingredient in marijuana, "hijacks and corrupts" the naturalprocess of endocannabinoids, a key family of chemicals that help guidethe brain in proper maturation, says Ruben Baler, a neuroscientist withthe National Institute on Drug Abuse (NIDA). These chemicals "play keyroles in memory formation, learning, decision-making," says Baler.

Noteveryone who uses marijuana regularly experiences problems withthinking and memory, says Roffman. But researchers have not been able topredict which users will and which won't.

"One of the maincontributors to worse outcomes (of marijuana use) is the age at whichyou start," says Baler. "So we are particularly worried about youngpeople who are using the drug."

The concern, especially for youngpeople, "is that you're performing suboptimally during those years whenyou should be working at peak levels of performance," he says. And withday-after-day use, the drug has a cumulative effect on achievement.Studies show that when marijuana is used chronically, "people achievelower in academics, job performance and life satisfaction," says Baler."It's difficult to understand why kids working so hard on theireducation would engage in an act that would lower their chance ofsuccess."

And, yes, marijuana is addictive, adds Baler. Accordingto the NIDA, about nine percent of people who use marijuana becomedependent on it. The number increases to about 1 in 6 among those whostart using it at a young age, and to 25% to 50% among daily users.

Thosewho become addicted can become quite ill when they try to quit. "Thereare many people who go into treatment to get over an addiction tomarijuana," says Baler.

Washington and Colorado became the firststates to vote to decriminalize the possession of an ounce or less ofmarijuana by adults 21 and older. Colorado's law is scheduled to takeeffect by Jan. 5.

More research is needed on how marijuana affectspeople of different ages and backgrounds, Roffman says. "There isevidence of genetic vulnerability to dependence. It is still at an earlystage of being studied."

Certain health conditions also putpeople at higher risk of problems. For example, people withcardiovascular disease will be at increased risk of a heart attack, hesays.

More than 29 million Americans ages 12 and older - 11.5% - reported using marijuana within the past year, according to NIDA numbers for 2010. That's a significant increase over numbers reported each year from 2002 to 2008.

Here'swhat the institute says is known about the effects of the drug, ashredded green and brown mix of flowers, stems, seeds and leavesderived from the hemp plant Cannabis sativa.

NIDA says thatmarijuana's main psychoactive ingredient, tetrahydrocannabinol (THC),binds to cannabinoid (CB) receptors, widely distributed throughout thenervous system and other parts of the body. In the brain, CB receptorsare found in high concentrations in areas that influence pleasure,memory, thought, concentration, sensory and time perception, appetite,pain and movement coordination.

That's why marijuana can have wide-ranging effects, including:

  • Impaired short-term memory. Marijuana use can make it hard to learn and retain information, particularly complex tasks.
  • Slowed reaction time and impaired motor coordination. It can throw off athletic performance, impair driving skills and increase risk of injuries.
  • Altered judgment and decision making. Experts say this can contribute to high-risk sexual behaviors that could lead to the spread of sexually transmitted diseases.
  • Increased heart rate. It can jump by 20% to 100%, which may increase the risk of heart attack, especially in otherwise vulnerable individuals.
  • Altered mood. In some, marijuana can induce euphoria or calmness; in high doses it can cause anxiety and paranoia.

The agency says long-term marijuana abuse can lead to:

  • Addiction.
  • Poorer educational outcomes, poorer job performance and diminished life satisfaction.
  • Respiratory problems (chronic cough, bronchitis).
  • Risk of psychosis in vulnerable individuals.
  • Cognitive impairment persisting beyond the time of intoxication.

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