Progression in substance use initiation: A multilevel discordant monozygotic twin design.

Progression in substance use initiation: A multilevel discordant monozygotic twin design.

Considerable attention has been paid to the "gateway" pattern of drug use initiation in which individuals progress from tobacco and alcohol use to cannabis and other illicit drugs. The extent to which this sequence reflects a causal impact of licit substance use on illicit substance involvement remains unclear. Clarifying the mechanisms underlying substance use initiation may help inform our un...

Journal of Abnormal Psychology Progression in Substance Use Initiation: A Multilevel Discordant Monozygotic Twin Design

Substance use and sexual intercourse onsets in adolescence: a genetically informative discordant twin design.

PURPOSE Using a genetically informed, discordant twin analysis, the objective of this study was to examine whether earlier onset of drinking and smoking behaviors predicted early sexual intercourse onset. METHODS Over 3,400 adult same-sex twins from the Australian Twin Registry completed a structured interview that included retrospective reports on onsets of smoking, drinking, intoxication, a...

McCune-Albright syndrome in a discordant monozygotic twin.

BACKGROUND McCune-Albright syndrome is a sporadic disorder characterized by polystotic fibrous dysplasia, pigmented patches of skin, and endocrinological abnormalities. OBJECTIVES To compare the genetic characteristics of the GNAS1 gene in a monozygotic pair of twins, one of whom was diagnosed with MAS while the other had no indication of the syndrome. METHODS We performed a molecular analy...

Risk factors for myopia in a discordant monozygotic twin study.

PURPOSE Monozygotic (MZ) twin pairs discordant for disease allow careful examination of environmental factors whilst controlling for genetic variation. The purpose of this study was to examine differences in environmental risk factors in MZ twins discordant for myopia. METHODS Sixty four MZ twin pairs discordant for refractive error were interviewed. Discordant twins were selected from 1326 M...