The Southern California Twin Register at the University of Southern California: II

Abstract

The Southern California Twin Register was initiated in 1984 at the University of Southern California, and continues to grow. This article provides an update of the register since it was described in the 2002 special issue of this journal. The register has expanded considerably in the past 4 years, primarily as a result of recent access to Los Angeles County birth records and voter registration databases. Currently, this register contains nearly 5000 twin pairs, the majority of whom are school age. The potential for further expansion in adult twins using voter registration records is also described. Using the Los Angeles County voter registration database, we can identify a large group of individuals with a high probability of having a twin who also resides in Los Angeles County. In addition to describing the expansion of register, this article provides an overview of an ongoing investigation of 605 twin pairs who are participating in a longitudinal study of behavioral problems during childhood and adolescence. Characteristics of the twins and their families are presented, indicating baseline rates of conduct problems, depression and anxiety disorders, and attention-deficit/hyperactivity disorder diagnoses which are comparable to non-twins in this age range.

Genetic and environmental bases of childhood antisocial behavior: A multi-informant twin study.

“…The details of the protocol can be found in Baker et al (2006). Briefly, the visit included behavioral interviews, neurocognitive testing, social risk factor assessment, and psychophysiological recording of the twins.…”

“…Comprehensive assessment of each child was made, including cognitive, behavioral, psychosocial, and psycho-physiological measures based on individual testing and interviews of the child and primary caregiver during the laboratory visit, with additional teacher surveys completed and returned by mail. A detailed description of the study, including a summary of the measures, can be found in Baker, Barton, Lozano, Raine, and Fowler (2006).…”

“…Study participation required that the twins be (a) proficient in English and (b) 9 or 10 years old at first assessment (see Baker et al, 2006). In addition, either English or Spanish proficiency was required for the twins' primary caregiver.…”

Genetic and environmental influences on nutrient intake

“…During Wave I (2001Wave I ( -2004) the twins were 9-10 years old (mean age = 9.60, SD = 0.59); during Wave II (2003II ( -2006) the twins were 11-13 years old (mean age = 11.79, SD = 0.92); during Wave III (2006-2010) the twins were 14-16 years old (mean age = 14.87, SD = 0.87); and during Wave 4 (2008-2011) the twins were 17-18 years old (mean age = 17.28, SD = 0.77). The total study sample includes 1,562 subjects, including 169 monozygotic (MZ) male, 171 MZ female, 121 dizygotic (DZ) male, 120 DZ female, and 200 DZ opposite-sex twin pairs (Baker et al 2006). The present study used data from Wave 2, as information on nutrients was not collected during Wave 1.…”

“…When both questionnaire and DNA results were available, there was a 90 % agreement between the two. Complete details on the procedures and measures can be found elsewhere (Baker et al 2006). …”