Varenicline for Light Smokers (ChanLight)

Inclusion Criteria:

1. Subjects must be ≥ 18 years of age;
2. smokes 5 to 10 CPD for at least 6 months;
3. express interest in quitting smoking;
4. indicate ability to complete all study visits; and
5. provide written informed consent to participate in the study.
6. Subject is a female subject of non-childbearing potential or a female subject of childbearing potential - who is using contraceptives and has a negative pregnancy test result;
7. Subject is in good health as determined by the investigator;
8. Subject has the ability to participate fully in all aspects of the study and keep scheduled appointments.

Exclusion Criteria:

1. An active medical condition such as unstable angina, myocardial infarction, or coronary angioplasty within the past 3 months or an untreated cardiac dysrhythmia;
2. History of renal failure;
3. Cancer [excluding non-melanoma skin cancer] not in remission;
4. Psychosis or bipolar disorder;
5. Current unstable or untreated moderate or severe depression as assessed by the CES-D;
6. have, as defined by the C-SSRS (Columbia-Suicide Severity Rating Scale), current non-specific suicidal thoughts, or have a lifetime history of a suicidal attempt (defined as "potentially self-injurious act committed with at least some wish to die, as a result of act.");

7. Substance dependence other than nicotine, defined as:

   a. Patient has a recent history (past month) of heavy alcohol consumption as defined by NIAAA: i. Men: More than 4 drinks on any day or 14 per week ii. Women: More than 3 drinks on any day or 7 per week. b. Use of cocaine, heroin, club drugs (i.e., MDMA/"ecstasy"), methamphetamine, or hallucinogens (e.g., LSD) at any time during the past month.

   c. Use of marijuana on a weekly basis for the past month

8. An allergy to varenicline;
9. Current use of a behavioral or pharmacologic tobacco dependence treatment and unwilling or unable to discontinue use;
10. Another member of their household already participating in this study; and
11. Current treatment with another investigational drug (within 30 days of study entry).
12. Has an unstable medical condition;
13. Subject has untreated hypertension or baseline systolic blood pressure > 180 or diastolic > 100;
14. Women of child-bearing potential, or who are pregnant, lactating or likely to become pregnant during the trial and are unwilling to use an acceptable form of contraception during the medication phase will also be excluded. All female subjects of childbearing potential must have a negative pregnancy test and must agree to use approved contraception during participation in the study.