title: Addictions and their familiality in Iceland.
abstract: Here, we provide an overview of previous family studies of addiction and present a new family study based on clinical data for more than 19,000 individuals who have been treated for addiction in Iceland over the last three decades. Coupled with the extensive Icelandic genealogy information, this population-based sample provides a unique opportunity for family studies. The relative risk (RR) was determined for up to fifth-degree relatives of probands diagnosed with alcohol, cannabis, sedative, and amphetamine dependence. We observe highly significant RR values for all substances ranging from 2.27 for alcohol to 7.3 for amphetamine, for first-degree relatives, and RRs significantly above 1 for distant relations, where the effect of shared environmental factors is minimized. The magnitude of risk in psychostimulant dependence is particularly striking. These findings emphasize the role of genetics in the etiology of addiction and highlight the importance of substance-specific effects.
authors.affiliation: SAA Treatment Center, Reykjavik, Iceland.
authors.forename: Thorarinn
authors.initials: T
authors.lastname: Tyrfingsson
authors.forename: Thorgeir E
authors.initials: TE
authors.lastname: Thorgeirsson
authors.forename: Frank
authors.initials: F
authors.lastname: Geller
authors.forename: Valgerdur
authors.initials: V
authors.lastname: Runarsdóttir
authors.forename: Ingunn
authors.initials: I
authors.lastname: Hansdóttir
authors.forename: Gyda
authors.initials: G
authors.lastname: Bjornsdottir
authors.forename: Anna K
authors.initials: AK
authors.lastname: Wiste
authors.forename: Gudrun A
authors.initials: GA
authors.lastname: Jonsdottir
authors.forename: Hreinn
authors.initials: H
authors.lastname: Stefansson
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Gulcher
authors.forename: Hogni
authors.initials: H
authors.lastname: Oskarsson
authors.forename: Daniel
authors.initials: D
authors.lastname: Gudbjartsson
authors.forename: Kari
authors.initials: K
authors.lastname: Stefansson
mesh_terms: D000437:Alcoholism / Q000235:genetics; D019969:Amphetamine-Related Disorders / Q000235:genetics; D019970:Cocaine-Related Disorders / Q000235:genetics; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D005789:Genealogy and Heraldry; D006801:Humans; D006993:Hypnotics and Sedatives; D007055:Iceland / Q000453:epidemiology; D008297:Male; D002189:Marijuana Abuse / Q000235:genetics; D008393:Marriage; D009293:Opioid-Related Disorders / Q000235:genetics; D010287:Parent-Child Relations; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000235:genetics* / Q000628:therapy
chemical_list: D006993:Hypnotics and Sedatives