Meta-analysis with dependent samples

#1
Dear Forum,

for my thesis I would like to conduct a meta-analysis with the aim to summarize the findings about the effectiveness of a political measure. The corresponding studies compare countries in which the measure was implemented with countries in which it was not implemented and calculate t-tests for various outcomes (e.g. robberies per million population).

The problem is that the studies have a more or less large overlap in their sample. The sample consists of individual countries, of which there is of course only a limited number. Therefore, some countries appear in several studies (e.g. a total of 25 countries are examined, in the next study 42, where a part of the 25 are included etc.) Sometimes the data come from different years, but sometimes they are exactly the same data because they were taken from a public database. Thus, the effect sizes are not independent of each other.

Is it even possible to deal with this kind of independence and calculate a meta-analysis in this case?

Thanks a lot and kind regards,
LC