Although the MSUTR began as a university-based twin registry assessing undergraduate men and women, we have been recruiting twins via birth records since the start of 2004. The Michigan Department of Community Health (MDCH) identifies twin pairs residing in Michigan who meet our study age criteria (see criteria below) and whose addresses or parents’ addresses (for twins who are minors) can be located using driver’s license information obtained from the state of Michigan. Twins are identified either directly from birth records or via the Michigan Twins Project, a large-scale twin registry within the MSUTR that doubles as a recruitment resource for smaller, more intensive projects. Because birth records are confidential in Michigan, recruitment packets are mailed directly from the MDCH to eligible twin pairs. Twins indicating interest in participation via pre-stamped postcards or e-mails/calls to the MSUTR project office are then contacted by study staff to determine study eligibility and to schedule their assessments.
Four recruitment mailings are used for each study to ensure optimal twin participation. Overall response rates across studies (56–85%) are on par with or better than those of other twin registries that use similar types of anonymous recruitment mailings. In the one study that has been completed thus far (i.e., the population-based portion of the Twin Study of Behavioral and Emotional Development in Children, TBED C), participating families endorsed ethnic group memberships at rates comparable to area inhabitants (e.g., Caucasian: 86.4% and 85.5%, African American: 5.4% and 6.3% for the participating families and the local census, respectively). Similarly, 14.0% of families in this sample lived at or below federal poverty guidelines, as compared to 14.8% across the state of Michigan. A comparison of participating and non-participating twins and their families is presented inTable 1 . We conclude that our recruitment procedures appear to yield samples that are representative of both recruited families and the general population of the state of Michigan.
Four recruitment mailings are used for each study to ensure optimal twin participation. Overall response rates across studies (56–85%) are on par with or better than those of other twin registries that use similar types of anonymous recruitment mailings. In the one study that has been completed thus far (i.e., the population-based portion of the Twin Study of Behavioral and Emotional Development in Children, TBED C), participating families endorsed ethnic group memberships at rates comparable to area inhabitants (e.g., Caucasian: 86.4% and 85.5%, African American: 5.4% and 6.3% for the participating families and the local census, respectively). Similarly, 14.0% of families in this sample lived at or below federal poverty guidelines, as compared to 14.8% across the state of Michigan. A comparison of participating and non-participating twins and their families is presented in
