Table 3 Weighted odds ratios (95% confidence intervals) for depressive symptoms by subgroup of BMI according to quartiles of serum copper concentrations, NHANES (2011–2016)

< 25 kg/m²

Cu (µg/dL)

 Q1 (< 99.20)

ref

ref

ref

 Q2 (99.20–114.55)

2.028 (0.878, 4.687)

2.609 (1.076, 6.327) ^*

1.825 (0.703, 4.732)

 Q3 (114.56–133.60)

1.230 (0.483, 3.133)

1.730 (0.624, 4.797)

0.735 (0.228, 2.365)

 Q4 (> 133.60)

1.377 (0.611, 3.104)

2.020 (0.769, 5.309)

0.877 (0.325, 2.363)

 P for trend

0.683

0.221

0.348

25 to < 30 kg/m²

Cu (µg/dL)

 Q1 (< 99.20)

ref

ref

ref

 Q2 (99.20–114.55)

0.656 (0.293, 1.470)

0.616 (0.269, 1.409)

0.446 (0.185, 1.075)

 Q3 (114.56–133.60)

1.572 (0.720, 3.432)

1.422 (0.622, 3.252)

0.799 (0.355, 1.798)

 Q4 (> 133.60)

1.139 (0.525, 2.475)

0.928 (0.365, 2.361)

0.528 (0.212, 1.311)

 P for trend

0.336

0.728

0.313

≥ 30 kg/m²

Cu (µg/dL)

 Q1 (< 99.20)

ref

ref

ref

 Q2 (99.20–114.55)

1.216 (0.601, 2.460)

1.089 (0.531, 2.236)

0.979 (0.437, 2.196)

 Q3 (114.56–133.60)

4.032 (2.186, 7.438) ^***

2.997 (1.535, 5.849) ^**

2.699 (1.285, 5.667) ^*

 Q4 (> 133.60)

4.779 (2.558, 8.930) ^***

3.113 (1.410, 6.869) ^**

2.490 (1.026, 6.046) ^*

 P for trend

< 0.001

0.004

0.028