ways: they started smoking at an earlier age, smoke more cigarettes per day, have more cognitive deficits, have more comorbid psychiatric disorders, have more medical problems, and have lower levels of smoking-cessation self-efficacy.

Tobacco Use and Anxiety Disorders

Anxiety disorders affect 25% of people (more women than men) during their lifetime and thus make up the largest entity of psychiatric disorders in the United States (Breslau et al., 1991). Anxiety disorders defined in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders include generalized anxiety disorder (GAD), PTSD, agoraphobia, panic disorder, simple phobia, and social phobia (American Psychiatric Association, 2000).

According to data from the 2001–2002 NCS, the prevalence of nicotine dependence in those with any anxiety disorder is higher than that in the general population. Although the percentage of current smokers differs among disorders, from 31.5% for social phobia, to 44.6% for PTSD, to 54.6% for GAD, all of the rates are significantly higher than the 22.5% of current smokers who had no past or current psychiatric disorder (Lasser et al., 2000).

It has been suggested that nicotine dependence increases the risk of PTSD. Koenen et al. (2005) in a study of over 6,744 Vietnam veteran twins found that nicotine dependence almost doubled the risk of developing PTSD in men exposed to trauma compared with the risk in nonsmokers. The prevalence of nicotine dependence was 71.2% in veterans who had PTSD compared with 40% in those who did not. Shared genetic effects accounted for about 63% of the association. Trauma alone and PTSD were associated significantly but less strongly than with nicotine dependence. Alterations in the function of the hypothalamic-pituitary-adrenal (HPA) axis seen in people who have PTSD may increase the risk of nicotine dependence. In a review of the neurobiologic association between smoking and PTSD, Rasmusson et al. (2006) suggested that activation of the HPA axis in response to a threat or stress releases neurohormones that can lead to arousal and anxiety. This dysfunction in areas of the brain that modulate reward, that is, the frontal lobe, hippocampus, and nucleus accumbens, is purported to promote nicotine dependence.

Tobacco Use and Depression

Depression is a common psychiatric disorder with a variety of subtypes and severity levels. Among patients who have depression, over 30% are daily smokers—a higher rate compared with that in the general

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