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. Author manuscript; available in PMC: 2017 Jun 1.
Published in final edited form as: Genes Brain Behav. 2016 Jun;15(5):503–513. doi: 10.1111/gbb.12296

Table 2.

Descriptive characteristics of studies included in meta-analysis

Study Year Age Sex (%female) Ancestry Country of Origin Allele frequency Total N
Met/Met Val/Met Val/Val
Lancaster et al 2012 22.7 ±4.2 61.42% European England 19 25 26 70
Goetz et al 2013 21.3 ±2.7 59.32% European-American United States 14 28 17 59
Lancaster et al 2015 22.2 ±4.6 43.56% European England 24 54 20 98
Current Mauscript 21.8 ± 3.9 64.9% European-American United States 55 97 56 208