SLC6A4 and Anxiety: Specifically, anxiety in association with sleep-related disturbances may be a driver for migraine development and transformation due to shared pathophysiological pathways: a polymorphism in the 5-HT transporter gene and a specific dopamine D2 receptor genotype, an imbalance of serotonin neurotransmitters as well as a disproportion between pro-inflammatory and anti-inflammatory cytokines in the hypothalamic-pituitary adrenal axis may account for the simultaneous presence of these comorbidities [3, 35].