It is important to note that although the correlation between FTCD and CPD is relatively high, the slight change of phenotype from FTCD-based nicotine dependence to CPD changes the results of the study. This has implications in other fields of medicine, implying that a small change in phenotype may expose previously undiscovered variants, and these variants may have specific roles in distinguishing differences between the two phenotypes. Rather than focusing only on increasing the sample size via meta-analyses, this study shows that samples with precise phenotypes may find previously undiscovered variants by conducting association studies using secondary phenotypes.
