Table 1.
Polychoric correlations for migraine and depression according to twin zygosity
| Two category broad classification* | |||||
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| Broad migraine | |||||
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| Zygosity [N] | MZFF [1623] | MZMM [833] | DZFF [1064] | DZMM [589] | DZFM [1210] |
| ρpolychoric (sd) | 0.45 (0.03) | 0.43 (0.05) | 0.31 (0.05) | 0.25 (0.07) | 0.12 (0.05) |
| 95% CI | (0.39–0.52) | (0.33–0.53) | (0.23–0.40) | (0.12–0.38) | (0.03–0.21) |
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| Broad depression | |||||
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| Zygosity [N] | MZFF [1623] | MZMM [833] | DZFF [1064] | DZMM [589] | DZFM [1210] |
| ρpolychoric (sd) | 0.43 (0.03) | 0.37 (0.05) | 0.10 (0.05) | 0.34 (0.06) | 0.13 (0.05) |
| 95% CI | (0.37–0.50) | (0.27–0.47) | (3×10−3–0.19) | (0.22–0.46) | (0.04–0.21) |
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| Three category broad classification^ | |||||
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| Broad migraine | |||||
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| Zygosity [N] | MZFF [1623] | MZMM [833] | DZFF [1064] | DZMM [589] | DZFM [1210] |
| ρpolychoric (sd) | 0.52 (0.02) | 0.42 (0.04) | 0.36 (0.03) | 0.30 (0.06) | 0.28 (0.04) |
| 95% CI | (0.47–0.57) | (0.33–0.51) | (0.30–0.43) | (0.19–0.41) | (0.21–0.36) |
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| Broad depression | |||||
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| Zygosity [N] | MZFF [1623] | MZMM [833] | DZFF [1064] | DZMM [589] | DZFM [1210] |
| ρpolychoric (sd) | 0.46 (0.03) | 0.37 (0.05) | 0.12 (0.04) | 0.29 (0.06) | 0.13 (0.04) |
| 95% CI | (0.40–0.52) | (0.28–0.47) | (0.04–0.21) | (0.17–0.40) | (0.05–0.22) |
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| Two category narrow classification# | |||||
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| IHS MO/MA | |||||
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| Zygosity [N] | MZFF [722] | MZMM [498] | DZFF [583] | DZMM [348] | DZFM [642] |
| ρpolychoric (sd) | 0.84 (0.03) | 0.69 (0.08) | 0.48 (0.06) | 0.50 (0.11) | 0.60 (0.06) |
| 95% CI | (0.79–0.89) | (0.54–0.84) | (0.36–0.59) | (0.29–0.71) | (0.49–0.71) |
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| MDD | |||||
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| Zygosity [N] | MZFF [1401] | MZMM [695] | DZFF [902] | DZMM [512] | DZFM [1024] |
| ρpolychoric (sd) | 0.53 (0.03) | 0.45 (0.06) | 0.15 (0.05) | 0.30 (0.07) | 0.16 (0.05) |
| 95% CI | (0.47–0.60) | (0.34–0.55) | (0.05–0.25) | (0.16–0.44) | (0.06–0.26) |
ρ polychoric: polychoric correlation; 95% CI: 95% confidence interval; sd: standard deviation; MZFF: female MZ twins; MZMM: male MZ twins; DZFF: female DZ twins; DZMM: male DZ twins; DZFM: opposite-sex DZ twins; N: number of twin pairs.
Two phenotype categories for broad migraine: non-migraine and self-report/ID migraine/IHS MO/MA; two phenotype categories for broad depression: non-depressed and MiDD/MDD.
Three phenotype categories for broad migraine: non-migraine, self-report/ID migraine and IHS MO/MA; three phenotype categories for broad depression: non-depressed, MiDD and MDD.
Two phenotype categories for narrow migraine: non-migraine and IHS MO/MA; two phenotype categories for narrow depression: non-depressed and MDD.