The purpose of this study is to see whether adults who use e-cigarettes every day experience symptoms of nicotine withdrawal when they stop using e-cigarettes for 6 days.

Study Design: The investigators will recruit 120 individuals who are long-term daily and exclusive users of nicotine-containing e-cigarettes. Participants will be asked to use their own e-cigarette as usual during the first week of the study and to then stop their use of e-cigarettes for 6 days. The total study duration will be 14 days. Participants will be instructed to continue abstinence from other tobacco and nicotine products during the entire study. The investigators will use an escalating payment system with bonuses based on breath and urine samples to encourage compliance.

Every day during the study, participants will report e-cigarette and tobacco cigarette use and monitor symptoms of nicotine withdrawal via a phone call to an Interactive Voice Response system. Participants will attend 3 study visits each week to provide urine and breath samples to verify compliance, and to complete brief surveys.

Inclusion Criteria:

• 18 years or older
• Able to read and understand verbal English fluently
• US citizen or resident alien
• Primarily uses e-cigarette product types of refillable tanks or modified devices
• Uses nicotine-containing e-liquid
• Has baseline urinary cotinine concentration of > 100 ng/ml
• Has used e-cigarettes daily for the last 2 months
• Has a home or cell phone
• Agrees to abstain from tobacco, marijuana and other illegal drugs during study

Exclusion Criteria:

• Smoked > 5 tobacco cigarettes in the last month
• Used non-cigarette nicotine, tobacco or quit smoking products on >5 days in the past month
• Use of cannabis (either marijuana or synthetic cannabis) > 5 times in the past month or positive test for cannabis use at screening
• Current (last 6 months) Generalized Anxiety Disorder, Major Depressive Disorder, Attention Deficit Hyperactivity Disorder or moderate/severe Substance Abuse Disorder
• Multiple legal, social health, work or school problems in the past month due to alcohol or drug use
• Pregnant or breastfeeding
• Previously a participant in the current study
• Use of prescribed or non-prescribed psychoactive medication > 5 times in the past month
• Expired carbon monoxide level > 8ppm