I wish to transform the MD to standardized MD.
For pregabalin the mean difference is -33.14. As far as I understand one way to achieve the above is to calculate the pooled SD using the 95% confidence interval estimate(s).
SD = (-53.98-(-33.14))/1.96*sqrt(235+151) = 208.898
Hence, the Cohen´s d is 33.14/208.898=0.15864.
Is my interpretation valid or should I use the raw data (means and SDs) from each study to estimate the standardized effect size?