Smoking is a form of substance use known for its ability to trigger a wide range of serious and potentially fatal health problems. In fact, current figures indicate that roughly 20 percent of all annual deaths in the U.S. stem from smoking-related causes. In a large-scale study review slated for publication in 2014 in the journal World Psychiatry, researchers from Great Britain\u2019s Oxford University compared the life expectancy impact of heavy smoking to the life expectancy impact of a range of serious and relatively common mental illnesses. These researchers concluded that the presence of serious mental illness can reduce the average life span more than heavy cigarette use. In addition to the powerfully addictive main ingredient nicotine, cigarettes sold in the U.S. and other countries typically contain hundreds of chemicals that can have a negative impact on human health. Some of these chemicals appear naturally in tobacco, either before or after burning occurs. Others are added by cigarette manufacturers for purposes that may include developing a distinctive flavor profile for a specific brand or increasing the impact that nicotine has on the brain. Habitual smoking substantially increases the odds that you will develop a number of health problems that can either kill you directly or considerably shorten your life. Prominent among these problems are ailments caused by declining cardiovascular health, ailments caused by lung damage or declining lung function, cancers that can appear in organ systems throughout the body, declining immune system function and type 2 diabetes. Serious Mental Illness Serious mental illnesses are conditions that can significantly diminish the ability to maintain a sense of psychological\/emotional well-being, fully take part in everyday private and\/or social life or live independently without the aid of others. Specific illnesses that fit this definition include major depression (major depressive disorder), bipolar I disorder, panic disorder, schizophrenia, post-traumatic stress disorder (PTSD) and obsessive-compulsive disorder (OCD). The federal Substance Abuse and Mental Health Services Administration uses a project called the National Survey on Drug Use and Health to track the year-to-year frequency of serious mental illness in American adults. The latest figures from this survey, compiled for 2012, indicate that roughly 9.6 million adults qualified for the diagnosis of a serious mental illness at some point during that year. This number is equal to slightly more than 4 percent of the total adult population. Groups with the highest risks for serious mental illness include women, adults between the ages of 26 and 49, and people with an American Indian\/Native Alaskan racial\/ethnic background. Comparing the Life Span Impact In the study review scheduled for publication in World Psychiatry, the Oxford researchers reanalyzed the results of 20 previous reviews involving a total of 1.7 million people in order to compare the life span impact of heavy cigarette smoking to the life span impact of serious mental illness. Heavy smoking does not have an official definition; however, the term commonly refers to the consumption of five or more cigarettes per day. Identified causes of death or reduced life expectancy for people affected by a serious mental illness include substance abuse and other behaviors that substantially increase short- or long-term health risks, as well as suicide. The researchers concluded that the average heavy smoker dies about 10 years sooner than his or her age contemporaries who don\u2019t smoke. By comparison, people affected by schizophrenia die roughly 10 to 20 years sooner than their contemporaries unaffected by this mental illness. Other serious mental illnesses associated with a decline in life expectancy greater than that found among heavy smokers include bipolar disorder (a drop of nine to 20 years), recurring major depression (a drop of seven to 11 years) and various types of substance use disorder (a drop of nine to 24 years). In addition to involvement in risky behavior and suicide, the study\u2019s authors note that the life span-shortening effects of serious mental illness may stem in part from the generally poor attitudes that the public holds toward people living with such conditions; specifically, these attitudes may have a negative impact on treatment rates. Apart from any stigmatizing attitudes, people with serious mental health issues may seek treatment for physical complaints less often than people unaffected by such issues. It\u2019s also important to note that, for a number of potential reasons, people affected by serious mental illness engage in cigarette smoking more often than the rest of the adult population.