An Italian study of 110 patients with episodic and chronic cluster headache and 203 controls found a significant genetic association between ADH4 SNP rs1126671, which has been associated with alcohol dependence and other addictive behaviors (Luo et al., 2005; Preuss et al., 2011), and cluster headache (Rainero et al., 2010). Here, ADH4 is linked to alcohol dependence.