SNCA and cocaine dependence: Furthermore, a growing literature also suggests a role for alpha-synuclein in addiction (Boyer & Dreyer 2007); expression of alpha-synuclein is increased in brain reward areas of cocaine addicts (Mash et al. 2003; Qin et al. 2005) and following psychostimulant treatment in rodents (Brenz Verca et al. 2003; Fornai et al. 2005).