Initial analyses were conducted to determine the potential of the DSM-IV nicotine dependence diagnosis and each of its 14 dichotomously scored symptoms as assessed by the SSAGA to exhibit evidence of linkage. Using a variance components approach, SOLAR (Almasy and Blangero, 1998) estimates h2 by partitioning the trait relative pair covariance into additive genetic and environmental contributions while correcting for participants’ age and gender. The probability that h2 was greater than zero was determined using a Student's t-test, which was used to evaluate the potential of the nicotine dependence diagnosis and its constituent symptoms to detect linkage.
