title: Methodologic problems in matched-pair studies using twins.
mesh_terms: D000428:Alcohol Drinking; D000704:Analysis of Variance; D003371:Cough / Q000453:epidemiology; D005260:Female; D005824:Genetics, Behavioral; D006801:Humans; D008297:Male; D011247:Pregnancy; D012107:Research Design; D012907:Smoking; D014427:Twins / Q000523:psychology