38 We used the ICE procedure in Stata to obtain five imputed datasets (further details are available from the corresponding author).
Where there was incomplete indication of use of a resource (e.g. either number or duration of contacts was given, but not both), missing details were imputed using within-country, within-group median values for resource users with relevant data.
Missing data on cognitive ability tests other than Mill Hill Vocabulary (0.6 1.7% at baseline; 0.8 4.7% at year 4) were imputed, as described in detail previously [ 5].
Findings are comparable across different levels of correlation (R = 0.50, 0.74, 0.84 and 0.94), therefore the meta-analysis (and subsequent meta-regression analyses) are robust to the imputed R = 0.84 (full details of sensitivity analyses are presented in Additional file 1: Table S8 and S9).
The original genotype codes were 0, 1, and 2 for the three SNP genotypes, respectively, and for missing genotypes (< 1%), a non-integer between 0 and 2 had been imputed (see [ 20] for details).
Missing data for income and wealth were imputed by the SHARE team; further details of the multiple imputation procedure are provided elsewhere.
27 When the SDs of absolute changes from baseline were not available from individual trials, we imputed them as described in detail in the Cochrane Handbook.
Mean correct rates were calculated per SNP (across individuals) as the proportion of correctly imputed genotypes, and then averaged over all imputed SNPs (for details, see [ 25]).
In order to increase efficiency and minimize selection bias, we used multivariable multiple imputation to impute missing variables for eligible participants (detailed information is available in Web Appendix 1 and Web Table 1).
For this study, we used sequences from 5,224 women with MDD and 5,218 controls, and imputed allele dosages at 6,242,619 SNPs across the nuclear genome (details on imputation methodology and genotype quality are given in [ 7]).
