Smoking Cessation With Varenicline in Schizophrenia: Antipsychotic-Induced Neurological Symptoms as Correlates

Inclusion Criteria: * DSM 5 criteria for schizophrenia or schizoaffective disorder and stable disease * Glazer-Morgenstern-Doucette criteria for TD * Smoking at least 5 cigarettes on average daily for at least 30 days prior to screening * An exhaled carbon monoxide concentration greater than 5 parts per million (ppm) at screening * Agree to stop smoking by the target date (four weeks after baseline * Concurrence for varenicline treatment from the patient's mental health provider if the patient is under mental health care; OR, if the patient is not under mental health care, the prescribing clinician should consult with a mental health provider to evaluate the patient for appropriateness to receive varenicline Exclusion Criteria: * Have untreated or unstable acute medical or psychiatric illnesses * Have a history of seizures * History of somnambulism * Have chronic degenerative neurological illnesses (e.g., Parkinson's disease) * Have a history of active substance abuse (including marijuana abuse) in the 3 months prior to screening or a positive toxicology screen * Are receiving clozapine or cholinesterase inhibitors * Had a change in dosing or medication type of antipsychotic or anti-muscarinic for one month prior to enrollment (two months for long-acting antipsychotics) * Are unable to remain on a stable dose of antipsychotic or anti-muscarinic during the study period * Have acute suicidal ideation, intent or behavior within 12 months or risk based assessed on the C-SSRS or depression/anxiety score ≥ 8 on the HADS. * Female subjects of childbearing age will have a negative pregnancy serum test at screening and are required to use approved methods of birth control * Use of an investigational drug within 30 days of screening * Use of other smoking cessation aids (bupropion, nicotine replacement products) * Use of other tobacco products * History of allergic reactions to varenicline * Lack capacity to provide informed consent