A Swedish national adoption study of criminality.
Level 3 - non-randomized controlled study
Nationwide observational adoption cohort study linking national registries
PubMed 24180693 · doi:10.1017/S0033291713002638
What was done
Researchers evaluated the contribution of genetic and environmental factors to criminal behavior (CB), including violent (VCB) and non-violent (NVCB) subtypes, using Swedish national registries. The sample comprised 18,070 adoptees born between 1950 and 1991, along with 79,206 biological relatives and 47,311 adoptive relatives. Criminal behavior was determined via conviction records in the Swedish Crime Register. Risk indices were constructed based on biological family history (CB and alcohol abuse) and adoptive family environment (CB, parental divorce, death, and medical illness).
What was found
Adoptees with at least one biological parent with a CB conviction had an increased risk of CB (OR 1.5, 95% CI 1.4–1.6). Elevated risk was also observed in biological full siblings (OR 1.4, 95% CI 1.2–1.6) and biological half-siblings (OR 1.3, 95% CI 1.2–1.3) of adoptees with CB. Both genetic and environmental risk indices strongly predicted the probability of adoptee CB and acted additively. The transmission of genetic risk for violent versus non-violent criminal behavior demonstrated moderate subtype specificity.
Why it matters
This nationwide adoption study demonstrates that criminal behavior arises from additive contributions of both inherited liability and family environmental disruptions, rather than purely one or the other. It also indicates partially distinct genetic pathways for violent versus non-violent offending.
Limits
Criminality was defined strictly by official convictions in national registers, omitting undetected or unprosecuted offenses. The study relied on administrative and registry data from Sweden, which may not generalize to populations with different legal, social, or adoption systems. Specific effect sizes and odds ratios for the composite risk indices were not reported in the abstract.
Cited by
- supports Scandinavian adoption and pedigree studies show that having a biological parent with alcohol addiction increases an offspring's likelihood of having multiple sexual partners, conduct disorder, or violent crime arrests, even when reared apart.