title: 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.
authors.affiliation: Department of Psychology, University of Southern California, Los Angeles, CA 90089, USA. lbaker@usc.edu
authors.forename: Laura A
authors.initials: LA
authors.lastname: Baker
authors.forename: Mafalda
authors.initials: M
authors.lastname: Barton
authors.forename: Dora Isabel
authors.initials: DI
authors.lastname: Lozano
authors.forename: Adrian
authors.initials: A
authors.lastname: Raine
authors.forename: James H
authors.initials: JH
authors.lastname: Fowler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000987:Antisocial Personality Disorder / Q000209:etiology; D002140:California; D002648:Child; D015331:Cohort Studies; D004200:Diseases in Twins / Q000209:etiology; D005260:Female; D005824:Genetics, Behavioral; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries / Q000706:statistics & numerical data; D012307:Risk Factors; D018433:Twin Studies as Topic / Q000706:statistics & numerical data