Background: Research indicates that early tobacco initiation increases risk for dependence, but despite this, early initiation is associated with slower transitions to escalated tobacco use. In contrast to these findings, other studies suggest that rapid escalated tobacco use is associated with increased dependence outcomes. Methods: Our sample was comprised of 5668 twins (2834 twin-pairs, mean age: 26.89, s.d = 4.42, 53.67% female, 57.69% monozygotic) from Colorado and Minnesota twin cohorts. We assessed the associations between 1) age of tobacco initiation and the speed of transitions (latency) to tobacco problem use and dependence and the associations between 2) age of initiation and latencies to tobacco problem use and dependence with tobacco dependence symptom severity. To further understand the etiological unfolding of these processes, we conducted univariate twin models and causally informative co-twin control models. Results: After adjustment for covariates, we found that early tobacco initiation was associated with a slower transition from initiation to problem use but a faster transition from problem use to dependence. Additionally, we found that earlier initiation and faster transitions to tobacco problem use and dependence predicted greater tobacco dependence severity within twin pairs (consistent with causal influences). The contribution of shared genetic and environmental factors was also evident for these relationships. Conclusions: Our study further disentangles the role of early initiation with transition times to tobacco problem use and dependence. In addition to common risk factors, we found potential causal roles for early tobacco initiation and rapid escalated tobacco use with increased risk for tobacco dependence severity.
Bibliographical noteFunding Information:
Supported in part by National Institute of Health grants T32 DA 17637-14 (PI: John Hewitt), DA011015 (PI: John Hewitt) and DA03580 (Multiple PIs: Christian Hopfer, Michael Stallings and Tamara Wall), National Institute on Drug Abuse grants DA05147 (PI: William Iacono) and DA13240 (PI: William Iacono) and National Institute on Alcohol Abuse and Alcoholism grant AA009367 (PI: Matt McGue).
- Age of initiation
- Co-twin control
- Onset age
- Speed of transition
- Tobacco dependence