The enrollment goal for each group is 50 patients (total of 100 patients for the study). This calculation is based on the approximate number of 30 patients the investigators will need to achieve a sensitivity of β-endorphin changes of 5 pM being statistically significant to a p-value of<0.05 with 95% power. Based in our finding in mice, the investigators expect β-endorphin levels to vary between individuals, and the investigators have increased sample size by 70% from our calculations to account for deviations from our β-endorphin levels estimations. Additionally, the investigators have added patients to account for a number of patient dropping out of the study, since this is a long trial for patients requiring multiple blood draws.