I am new to meta-analysis. I am looking at the psychological symptoms that develop in healthy people when given a drug versus placebo. Different measurement scales are used -so I need to use SMD. There is a mixture of change data and absolute measurement data. Mostly absolute measurement data. I want do a metaregression for participant age etc I also have the problem that there is paired data and unpaired data- most of which is paired. What is the best way of calculating the effect size combining all this data. Or would it be better to not include change data and independent group data. The other thing to say is that in some of the studies have 0 as the s.d for the placebo group because well people dont have symptoms with placebo - so this data looks like change data.