Chunk #14 — RESULTS — Genetically informative research approaches and their limitations — Evidence for heritable influences on substance initiation and use
There is less evidence for the role of shared environmental influences on adolescent smoking. Several twin studies report that the heritability of smoking ranges from 25%32 to 80%,33 with higher heritability estimates for current smoking and regular or daily smoking. In contrast, Koopmans et al34 found no evidence for heritable influences of smoking in adolescents aged 12-14 years – heritability increased to 27% in women aged 15-16 years and to 30-60% at ages 17-25 years. To some extent, these discrepancies are attributable to variability in definitions of smoking. Likewise, modest genetic and prominent shared environmental factors have been noted as contributors to variation in initiation of cannabis and other illicit drugs.35
