Cognitive ability and risk for substance misuse in men: genetic and environmental correlations in a longitudinal nation-wide family study.
To investigate the association in males between cognitive ability in late adolescence and subsequent substance misuse-related events, and to study the underlying genetic and environmental correlations.



A population-based longitudinal study with three different family-based designs. Cox proportional hazards models were conducted to investigate the association at the individual level. Bivariate quantitative genetic modelling in (1) full brothers and maternal half-brothers, (2) full brothers reared together and apart and (3) monozygotic and dizygotic twin brothers was used to estimate genetic and environmental correlations.



Register-based study in Sweden.



The full sample included 1 402 333 Swedish men born 1958-91 and conscripted at mean age 18.2 [standard deviation (SD) = 0.5] years. A total of 1 361 066 men who had no substance misuse events before cognitive assessment at mandatory military conscription were included in the Cox regression models, with a follow-up time of up to 35.6 years.



Cognitive ability was assessed at conscription with the Swedish Enlistment Battery. Substance misuse events included alcohol- and drug-related court convictions, medical treatments and deaths, available from governmental registries.



Lower cognitive ability in late adolescence predicted an increased risk for substance misuse events [hazard ratio (HR) for a 1-stanine unit decrease in cognitive ability: 1.29, 95% confidence interval (CI) = 1.29-1.30]. The association was somewhat attenuated within clusters of full brothers (HR = 1.21, 95% CI = 1.20-1.23). Quantitative genetic analyses indicated that the association was due primarily to genetic influences; the genetic correlations ranged between -0.39 (95% CI = -0.45, -0.34) and -0.52 (95% CI -0.55, -0.48) in the three different designs.



Shared genetic influences appear to underlie the association between low cognitive ability and subsequent risk for substance misuse events among Swedish men.
Department of Public Health, University of Helsinki, Finland. antti.latvala@helsinki.fi.|Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. antti.latvala@helsinki.fi.
Antti
A
Latvala
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Ralf
R
Kuja-Halkola
Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.
Brian M
BM
D'Onofrio
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Department of Medical Sciences, Örebro University, Örebro, Sweden.
Henrik
H
Larsson
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Paul
P
Lichtenstein
D000293:Adolescent; D003072:Cognition Disorders / Q000150:complications* / Q000453:epidemiology; D059647:Gene-Environment Interaction; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010375:Pedigree; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000235:genetics / Q000523:psychology*; D013548:Sweden / Q000453:epidemiology; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
Cognitive ability; family study; longitudinal study; quantitative genetic analysis; register-based research; substance misuse