In this paper, we sought to understand what the biological mechanism of nightmares so that we could learn how to overcome and improve our quality of sleep. Previous research has predicted an increase in nightmares by variables such as sugar consumed prior to sleeping, an increase in serotonin levels, and frontal alpha asymmetry. In our correlational study, we tested the strength of these relationships by examining naturalistic daily changes in their variables longitudinally over a period of one week. We measured food by grams of sugar consumed prior to sleeping, serotonin levels by hours spent waking vs. sleeping, Frontal Alpha Asymmetry by frontal alpha cortical waves during resting wakefulness using a Muse headband, and nightmares by using the modified Differential Emotions Scale (see Appendix A). Data pooled across participants did not find nightmares were significantly correlated with any of the three predictor variables measured. These results suggest that those who seek to decrease nightmares should attempt to do so via methods other than manipulating sugar intake or hours of sleep. The biological cause of nightmares requires further research to be determined.