Ahrenfeldt L, Petersen I, Johnson W, Christensen K. Academic performance of opposite-sex and same-sex twins in adolescence: A Danish national cohort study. Horm Behav. 2015;69:123-31 pubmed publisher
..Scores for OS and SS males were similar in all topics. In conclusion, this study did not provide evidence for a masculinization of female twins with male co-twins with regard to academic performance in adolescence. ..
Petersen I, Pedersen N, Rantanen T, Kremen W, Johnson W, Panizzon M, et al. G×E Interaction Influences Trajectories of Hand Grip Strength. Behav Genet. 2016;46:20-30 pubmed publisher
..Though not statistically significant, the results suggested that APOE ɛ2ɛ2/ɛ2ɛ3 haplotypes might buffer environmental influences on grip strength trajectories. ..
Petersen I, Martinussen T, McGue M, Bingley P, Christensen K. Lower marriage and divorce rates among twins than among singletons in Danish birth cohorts 1940-1964. Twin Res Hum Genet. 2011;14:150-7 pubmed publisher
..The interpretation may be that since twins have a partner from birth, they do not have the same need for marriage as singletons but have more experience in maintaining a relationship if they do marry. ..