Controlling for baseline differences?

#1
I am comparing two groups, with data before and after retirement, to see the effect retirement has on depression levels.

The control group works over the two measurement points, and the retirees group works at baseline and retires at post.

Let's say I have the mean, SD and sample size of each of these groups pre/post retirement, how do I calculate the effect size for the change in depression levels for the retirees group, that controls for the differences in depression level between the groups at baseline?
 

hlsmith

Not a robit
#2
post_dep = Baseline_dep + retirement_status

Put in regression model. Are there other differences that need to be controlled for as well?
 
#3
post_dep = Baseline_dep + retirement_status

Put in regression model. Are there other differences that need to be controlled for as well?
Actually this is done in relation to a meta-analysis I am struggling to figure out.

Most of the included studies report data for the following:
Workers: Pre and post levels of depression
Retirees: Pre and post levels of depression

I have noticed though, that the groups differ significantly at the pre-measurement.

So I want to calculate the mean level of change for retirees when controlling for the level of change in the control group.