qRT-PCR analysis of mRNA levels of molecular elements of growth factor systems highly implicated in the pathophysiology of depression (Yu and Chen 2011; Clark-Raymond and Halaris 2013), namely brain-derived neurotrophic factor (Bdnf), vascular endothelial growth factor (Vegf) and their respective receptors was carried out in basolateral amygdala samples of Cry2−/− and Cry2+/+ mice (Supplementary Table 2a). Here, BDNF is linked to depressive symptom measurement.