Low Nicotine Cigarettes Plus Electronic Cigarettes

Inclusion Criteria: * Smoke \>5 cigarettes per day for at least the prior 12 months * Smoke regular, filtered cigarettes or machine-rolled cigarettes with a filter * Exhaled CO measurement of ≥ 6 parts per million at baseline * No serious cigarette smoking quit attempt or use of any FDA-approved smoking cessation medication in the prior 30 days (includes any nicotine replacement, varenicline, bupropion \[used specifically as a quitting aid\]) * No plans to quit smoking within the next 3 weeks * Must be willing to both switch to a different type of cigarette that may contain a different amount of nicotine and to try an e-cig to substitute for some of their cigarettes * Must be willing and able to respond to contacts from study staff or attend visits over the study period (not planning to move, not planning extended vacation, no planned surgeries) * 9\. Must meet lifetime diagnostic criteria for a current or lifetime unipolar or bipolar mood disorder (e.g. major depressive disorder, major depressive episode, manic episode, hypomanic episode, bipolar disorder), an anxiety disorder (e.g. panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, , agoraphobia, social anxiety disorder, generalized anxiety disorder), a psychotic disorder (e.g. mood disorder or other psychotic disorder), or an eating disorder (e.g. anorexia or bulimia) based on the MINI-International Neuropsychiatric Interview Standard (MINI) (version 7.0.2) * Able to read and write in English * Able to understand and give informed consent * Access to a computer/smartphone with e-mail and a reliable internet connection Exclusion Criteria: * Women who are pregnant and/or nursing or trying to become pregnant * Unstable or significant medical condition in the past 3 months (e.g., recent heart attack or other serious heart condition, stroke, severe angina, high blood pressure \[systolic \>159 mmHg or diastolic \>99 mmHg during screening) * Respiratory diseases (e.g., exacerbations of asthma or COPD, require oxygen, require oral prednisone), kidney (e.g., dialysis) or liver disease (e.g., cirrhosis), severe immune system disorders (e.g., uncontrolled HIV/AIDS, multiple sclerosis symptoms) or any medical disorder/medication that may affect participant safety or biomarker data * Uncontrolled mental illness or substance abuse, or inpatient treatment for these in the past 6 months * Current suicide risk on clinical assessment (above "low risk" score (or ≥ 9) on MINI diagnostic interview suicide module during screening (34)) * Use of any non-cigarette nicotine delivery product (e.g., pipe, cigar, dip, chew, snus, hookah, e-cig, strips or sticks, IQOS) in the past 7 days at screening * Use of an e-cig for 5 or more days in the past 28 days or any use in the past 7 days at screening * Use of marijuana or other illegal drugs/prescription drugs for non-medical use daily/almost daily or weekly in the past 3 months per NIDA Quick Screen * Any known allergy to propylene glycol or vegetable glycerin * Surgery requiring general anesthesia in the past 6 weeks * Unwilling to remain on one flavor of cigarette (regular or menthol) for the duration of the trial * Previous use of SPECTRUM research cigarettes in the past 6 months * Other member of household currently participating in the study * History of a seizure disorder or had a seizure in the past 12 months * Currently taking or have taken medications prescribed to prevent seizures (such as Carbamazepine or Phenobarbital). Using seizure medications for off-label use (indications other than treatment for seizures) will not be included as an exclusion, these will be assessed on a case-by-case basis