Considering all we know about cigarettes and their scary health effects, why would anyone start smoking them? While it's impossible to pinpoint a single reason for why any one person begins, a new study identifies three risk factors for taking up the habit.

The study, conducted by researchers at the University of Montreal School of Public Health, suggests that for people between the ages of 18 and 24, the three biggest risk factors for starting smoking are being impulsive, using alcohol regularly, and getting poor grades in school.

The research, published in the Journal of Adolescent Health, is based on data from 1,293 teens from the greater Montreal area who were part of the Nicotine Dependence in Teens study that started in 1999. The teens were followed up in 22 "cycles," from when they were at an average age of 12.7 to when they were at an average age of 24.

By cycle 22, 75 percent of the teens had tried smoking. Forty-four percent of the teens started smoking before entering high school, 43 percent started during high school, and 14 percent started sometime in the six years post-high school.

Not all those who tried cigarettes continued to smoke, but researchers found that impulsivity, poor grades and regular alcohol use were the three risk factors associated with those who began smoking after high school -- or when they were between ages 18 and 24.

Study researcher Jennifer O'Loughlin, a professor at the university, speculated in a statement that one potential reason impulsivity may play a role in smoking in young adulthood is because "parents of impulsive children exercise tighter control when they are living with them at home to protect their children from adopting behaviors that can lead to smoking, and this protection may diminish over time."

Alcohol consumption could also be linked with starting smoking because alcohol "reduces inhibitions and self-control," she added in the statement.

O'Loughlin noted that the findings suggest smoking prevention programs shouldn't just target teens, but young adults also. "The predictors of initiation in young adults may provide direction for relevant preventive interventions," she and co-authors wrote in the study.

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  • You'll Be Less Anxious

    Even though smokers may believe taking a long drag on a cigarette can help to calm nerves, a British study published earlier this year suggests that <em>quitting</em> can actually decrease anxiety more over the long-term. "People who achieve abstinence experience a <a href="http://www.cbc.ca/news/health/story/2013/01/02/smoking-quit-anxiety.html">marked reduction in anxiety</a> whereas those who fail to quit experience a modest increase in the long term," researchers wrote in the British Journal of Psychiatry study, as reported by CBC News. Similarly, a 2010 study in the journal Addiction showed that <a href="http://www.reuters.com/article/2010/06/17/us-smoking-idUSTRE65G0CX20100617">perceived stress decreased</a> for people who quit smoking for a year after hospitalization for heart disease, Reuters reported.

  • Your Mouth Will Thank You

    Quitting the habit could dramatically <a href="http://consumer.healthday.com/Article.asp?AID=661533">decrease your risk of dental problems</a> like cavities and gum disease, and even more dangerous conditions like oral cancer, according to a study from the Centers for Disease Control and Prevention. HealthDay reported that <a href="http://consumer.healthday.com/Article.asp?AID=661533">compared with former smokers</a>, smokers have a 1.5-times higher risk of developing at least three oral health conditions.

  • Your Sex Life Will Be Better

    Here's a bedroom-related reason to quit smoking: studies have suggested a link between smoking and decreased sex drives for both men <em>and</em> women. Studies published in 2008 in the Journal of Sexual Medicine showed that nicotine can affect even <a href="http://www.ncbi.nlm.nih.gov/pubmed/17971108">nonsmoking men's</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/18331269">women's sexual arousal</a>. And if that's not enough to convince you, well, there's also <a href="http://healthland.time.com/2011/09/15/guys-quitting-smoking-makes-it-bigger-really/">this</a>.

  • You'll Save Your Skin

    If you want your skin to be at its best, then you're better off quitting cigarettes. WebMD points out that smoking <a href="http://www.webmd.com/smoking-cessation/ss/slideshow-ways-smoking-affects-looks">affects skin tone</a>, promotes sagginess and, of course, causes those wrinkles around the lip area. However, the American Society for Aesthetic Plastic Surgery notes that just a month-and-a-half after <a href="http://www.surgery.org/consumers/plastic-surgery-news-briefs/skin-quit-smoking-1031403">quitting smoking</a>, your skin will already begin to look better.

  • You'll Have More Locks

    If you love your hair, maybe it's time to put the cigarettes down. Research has linked smoking with an increased risk of male pattern baldness. BBC News reported in 2007 on a Archives of Dermatology study, showing even after taking into account other hair-loss risk factors like age and race, <a href="http://news.bbc.co.uk/2/hi/health/5413382.stm">heavy smoking</a> (at least 20 cigarettes daily) raised the risk of baldness. And a 2011 study showed that smoking, stress, drinking and genes were all<a href="http://www.webmd.com/skin-problems-and-treatments/hair-loss/news/20110923/divorce-heavy-drinking-smoking-linked-to-hair-loss"> risk factors for baldness</a>, WebMD reported.

  • Your Mood Will Improve

    Here's a pretty good benefit: Stopping smoking could <a href="http://news.brown.edu/pressreleases/2010/12/smoking">make you a happier person</a>, according to research from Brown University. Researchers there found that smokers were <a href="http://news.brown.edu/pressreleases/2010/12/smoking">never happier</a> than when they were quitting smoking, even if they went back to smoking afterward. According to a <a href="http://news.brown.edu/pressreleases/2010/12/smoking">news release</a>: <blockquote> The most illustrative — and somewhat tragic — subjects were the ones who only quit temporarily. Their moods were clearly brightest at the checkups when they were abstinent. After going back to smoking, their mood darkened, in some cases to higher levels of sadness than before.</blockquote>

  • You'll Have More Birthdays

    Stopping smoking may <a href="http://www.huffingtonpost.com/2012/10/29/women-stop-smoking-live-10-years-longer_n_2011804.html">help women live a decade longer</a> than they would have if they had continued lighting up, according to a 2012 study in The Lancet. Researchers also found that the more the women smoked, the higher their risk of premature death, with even "light" smokers (those who smoked just one to nine cigarettes a day) having a doubled risk of death compared with non-smokers. "If women smoke like men, they die like men -- but, whether they are men or women, smokers who stop before reaching middle age will on average <a href="http://www.eurekalert.org/pub_releases/2012-10/l-soa102312.php">gain about an extra ten years of life</a>," study researcher Professor Sir Richard Peto, of the University of Oxford, said in a statement.

  • You'll Improve Your Pregnancy Chances

    If you're trying to conceive, one of the best things you can do is to quit smoking, research shows. NBC News reported that women smokers have a 60 percent <a href="http://today.msnbc.msn.com/id/16874634/ns/today-today_health/t/trying-conceive-quit-smoking/#.UOr-7onjlU4">higher chance of being infertile</a>, compared with nonsmokers. Smoking is also linked to more spontaneous miscarriages, according to NBC News.

  • You'll Enjoy Food More

    If you <a href="http://abcnews.go.com/Health/Healthday/story?id=8427779#.UOsAFInjlU4">don't like bland food</a>, then don't smoke, research suggests. A small 2009 study of Greek soldiers shows an association between smoking and <a href="http://www.eurekalert.org/pub_releases/2009-08/bc-stf081809.php">"fewer and flatter" taste buds</a>, according to a statement on the research.

  • Your Colds Won't Be As Bad

    Mild cold symptoms could take on a more serious form for smokers, according to a study from Yale University researchers. The findings, published in 2008 in the Journal of Clinical Investigation, showed an <a href="http://news.yale.edu/2008/07/24/study-shows-why-cigarette-smoke-makes-flu-other-viral-infections-worse">overreaction of the immune systems</a> of cigarette smoke-exposed mice when exposed to a virus similar to the flu. "The anti-viral responses in the cigarette smoke exposed mice were not only not defective, but were hyperactive," study researcher Dr. Jack A. Elias, M.D., said in a statement. "These findings suggest that smokers do not get in trouble because they can't clear or<a href="http://news.yale.edu/2008/07/24/study-shows-why-cigarette-smoke-makes-flu-other-viral-infections-worse"> fight off the virus</a>; they get in trouble because they overreact to it."

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