The PALSPAC Twin Registry follows a population-based sample of over 400 families with child and adolescent twin pairs born in Pennsylvania in the United States of America. The initial recruitment effort, used from 2012 to 2014, recruited families with adolescent twins via Pennsylvania junior high/middle and high schools, alongside recruitment from birth records at a Pittsburgh hospital and on the online registry website. A second recruitment effort, beginning in 2019, aimed to recruit families with young children born from 2016 to 2017 who were identified from birth records.

Recruitment is ongoing