One clinical genetic study [30] showed no association between pre-proghrelin gene (GHRL) variations, and susceptibility to the development of methamphetamine dependence in a sample of Korean population, but found a significant correlation between carrying the GHRL single nucleotide (Leu72Met) polymorphism and emotional problems, such as depression or anxiety, which are associated with drug addiction. Here, GHRL is linked to depressive symptom measurement.