With regards to common control groups, you may want to check out 16.5.4 of the Cochrane Handbook. To quote a subset of this page:
Approaches to overcoming a unit-of-analysis error for a study that
could contribute multiple, correlated, comparisons include the
- Combine groups to create a single pair-wise comparison
- Select one pair of interventions and exclude the
- Split the ‘shared’ group into two or more groups with smaller
sample size, and include two or more (reasonably independent)
- Include two or more correlated comparisons and account
for the correlation.
- Undertake a multiple-treatments meta-analysis
(see Section 16.6).
The recommended method in most situations is to
combine all relevant experimental intervention groups of the study
into a single group, and to combine all relevant control intervention
groups into a single control group. As an example, suppose that a
meta-analysis of ‘acupuncture versus no acupuncture’ would consider
studies of either ‘acupuncture versus sham acupuncture’ or studies of
‘acupuncture versus no intervention’ to be eligible for inclusion.
Then a study comparing ‘acupuncture versus sham acupuncture versus no
intervention’ would be included in the meta-analysis by combining the
participants in the ‘sham acupuncture’ group with participants in the
‘no intervention’ group. This combined control group would be compared
with the ‘acupuncture’ group in the usual way. For dichotomous
outcomes, both the sample sizes and the numbers of people with events
can be summed across groups. For continuous outcomes, means and
standard deviations can be combined using methods described in Chapter
7 (Section 220.127.116.11).
With regards to pooling effect sizes for performing moderator meta analysis. There is a list of SPSS resources here. You might want to get a book like Introduction to Meta-Analysis to provide an overview of some of the many issues and calculations involved.
- Borenstein, M., Hedges, L.V., Higgins, J.P.T. & Rothstein, H.R. (2011). Introduction to meta-analysis. John Wiley \& Sons