Table 2.
Associations between access to green space and depression* among twin pairs in the University of Washington Twin Registry, 2008–2012
| Model A |
Model B |
Model C |
Model D |
Model E |
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Coef | 95% CI | Coef | 95% CI | Coef | 95% CI | Coef | 95% CI | Coef | 95% CI | |
| Fixed effects | ||||||||||
| NDVI† | ||||||||||
| Between-pair effect (βB) | −0.17 | −0.36 to 0.03 | −0.12 | −0.31 to 0.07 | −0.12 | −0.31 to 0.08 | −0.12 | −0.31 to 0.08 | −0.11 | −0.37 to 0.02 |
| MZ within-pair effect (βW) | −0.44 | −0.74 to −0.14 | −0.39 | −0.70 to −0.09 | −0.39 | −0.70 to −0.09 | −0.38 | −0.68 to −0.07 | −0.44 | −0.80 to −0.25 |
| DZ—MZ within-pair effect (βB) | 0.29 | 0.01 to 0.56 | 0.28 | 0.01 to 0.56 | 0.29 | 0.01 to 0.56 | 0.27 | −0.01 to 0.55 | 0.27 | −0.08 to 0.45 |
| Zygosity | −0.04 | −0.11 to 0.03 | −0.04 | −0.34 to 0.26 | −0.04 | −0.34 to 0.03 | −0.05 | −0.12 to 0.02 | −0.04 | −0.12 to 0.00 |
| Income | −0.05 | −0.06 to −0.04 | −0.05 | −0.06 to −0.04 | −0.05 | −0.06 to −0.04 | −0.05 | −0.06 to −0.04 | ||
| MVPA | −0.03 | −0.05 to −0.01 | −0.02 | −0.04 to 0.00 | ||||||
| Walking in neighbourhood‡ | −0.03 | −0.04 to −0.01 | −0.01 | −0.03 to 0.01 | ||||||
| Transit use | 0.00 | −0.02 to 0.02 | −0.01 | −0.02 to 0.01 | ||||||
| Singh Index§ | 0.00 | −0.05 to 0.03 | ||||||||
| Population density | 0.00 | 0 to 0 | ||||||||
| Random effects | ||||||||||
| Census tract | 0 | 0 | 0.00 | 0 to 0 | 0.00 | 0 to 0 | 0.00 | 0 to 0 | ||
| Between MZ pair | 0.21 | 0.16 to 0.26 | 0.19 | 0.15 to 0.24 | 0.20 | 0.15 to 0.24 | 0.20 | 0.16 to 0.25 | 0.19 | 0.13 to 0.22 |
| Within MZ pair | 0.68 | 0.63 to 0.73 | 0.67 | 0.62 to 0.72 | 0.67 | 0.62 to 0.72 | 0.66 | 0.61 to 0.71 | 0.68 | 0.62 to 0.71 |
| Between DZ pair | 0.02 | −0.06 to 0.10 | 0.02 | −0.07 to 0.10 | 0.02 | −0.07 to 0.11 | 0.03 | −0.05 to 0.12 | 0.01 | −0.09 to 0.06 |
| Within DZ pair | 0.92 | 0.81 to 1.02 | 0.91 | 0.80 to 1.02 | 0.91 | 0.80 to 1.02 | 0.90 | 0.79 to 1.00 | 0.91 | 0.78 to 0.97 |
*
Measured by the modified 2-item Patient Health Questionnaire.
†
Access to green space assessed by the Normalised Difference Vegetation Index (NDVI), a measure of ‘greenness’ using satellites to assess the density of vegetation in the target area.
‡
Walking rescaled to hours/week.
§
Neighbourhood deprivation assessed by the Singh Index, which combines data on education, employment, income and income disparity, poverty, characteristics of the home and home, vehicle, and telephone ownership.
DZ, dizygotic; MVPA, moderate-vigorous physical activity (rescaled to hours/week); MZ, monozygotic.