Defense Date


Document Type


Degree Name

Master of Science


Human Genetics

First Advisor

Elizabeth C. Prom-Wormley, PhD, MPH

Second Advisor

Hermine Maes, PhD

Third Advisor

Michael Neale, PhD


The purpose of this study was to examine the genetic and environmental influences on lifetime quit attempt in three US adolescent and young adult twin samples (N total = 6,322). The study utilized a common-contingent-causal (CCC) model to estimate these factors for lifetime quit attempts, after accounting for the factors for lifetime cigarette use and cigarettes per day. The study also examined age and sex differences, as well as the degree of relationship between these smoking phenotypes. The results demonstrated significant genetic influences for lifetime quit attempts in adolescents and young adults. No sex differences were observed for the contributions of genetic and environmental factors for lifetime quit attempts. Furthermore, separate liabilities for lifetime quit attempts and lifetime cigarette use were found for most age groups. Study findings have important implications for promoting quit attempts in adolescents and young adults.


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