Which Dopamine Polymorphisms Are Functional? Systematic Review and Meta-analysis of COMT, DAT, DBH, DDC, DRD1–5, MAOA, MAOB, TH, VMAT1, and VMAT2 - Tunbridge, E; Narajos, M; Harrison, C; Beresford, C; Cipriani, A; Harrison, P (Elsevier, 2019)