E-Cigarette Use Predicted Starting Marijuana Among Hispanic Young Adults Who Had Not Previously Used It | Research

The takeaway

Among Hispanic young adults who were not using marijuana in 2014, those who used e-cigarettes were nearly twice as likely to be using marijuana one year later compared to non-e-cigarette users.

Read this if you use e-cigarettes and want to understand whether they are associated with starting other substances.

E-cigarette users were 1.97x more likely to start marijuana and 3.32x more likely to start cigarettes within one year.

What the researchers found

Researchers followed 1,332 Hispanic young adults in Los Angeles over one year. Among those who were not using marijuana in 2014, e-cigarette users were nearly twice as likely to be using marijuana by 2015 (24% vs 12%, OR = 1.97).

The effect was even stronger for cigarette smoking: among non-smokers, e-cigarette users were over 3 times more likely to become smokers (26% vs 7%, OR = 3.32).

Importantly, among people who were already using marijuana or cigarettes, e-cigarette use was not associated with changes in use of either substance. E-cigarette use was also not associated with smoking cessation among current smokers.

This pattern suggests e-cigarettes may serve as a gateway to other substances for non-users but do not increase use among existing users or help smokers quit.

Why it matters

This is one of the first longitudinal studies to show that e-cigarette use predicts subsequent marijuana initiation, not just tobacco. The finding in a Hispanic young adult population is particularly important given disparities in substance use prevention and treatment access.

The numbers in context

1,332 Hispanic young adults. Past-month prevalence in 2014: e-cigarettes 9%, cigarettes 21%, marijuana 23%. Among marijuana non-users, e-cigarette users had 1.97x odds of starting marijuana. Among non-smokers, e-cigarette users had 3.32x odds of starting cigarettes.

How the study worked

Longitudinal survey study of 1,332 Hispanic young adults (59% female, mean age 22.7) in Los Angeles, California. Data collected in 2014 and 2015. Logistic regression examined whether e-cigarette use in 2014 predicted cigarette and marijuana use in 2015, controlling for age, sex, and other substance use.

What this study cannot tell us

Observational design cannot prove e-cigarettes caused subsequent substance initiation. Unmeasured confounders (risk-taking personality, peer environment) could explain the association. The sample was entirely Hispanic young adults in Los Angeles, limiting generalizability. Two time points one year apart may miss important temporal patterns.

How to read the evidence

Moderate evidence from a prospective longitudinal study with appropriate controls, though limited by the observational design and single demographic group.

When this study was published

Published in 2016. The e-cigarette landscape has changed dramatically since, with newer device types potentially altering these patterns.

The bigger picture

The "gateway" debate has historically focused on marijuana leading to harder drugs. This study suggests the gateway concept may need updating: e-cigarettes may serve as a gateway to both tobacco and marijuana, potentially lowering the barrier to inhaling substances for young people who might not have otherwise tried them.

Questions still open

Does the e-cigarette to marijuana pathway hold in other demographic groups? Is the association driven by shared social contexts or by nicotine exposure changing brain reward sensitivity? Would restricting e-cigarette access reduce marijuana initiation rates?

Common questions

Do e-cigarettes lead to marijuana use?

This study found that e-cigarette users were nearly twice as likely to start using marijuana within a year. However, this is an association, not proof of causation. It may be that people inclined to try new substances are drawn to both e-cigarettes and marijuana.

Do e-cigarettes help people quit smoking?

In this study, e-cigarette use among current smokers was not associated with smoking cessation one year later. Among non-smokers, e-cigarette use actually predicted starting cigarettes, suggesting a net negative public health effect in this population.

Read the original research

E-cigarette use and subsequent cigarette and marijuana use among Hispanic young adults.

Drug and alcohol dependence, 163, 261-4

View on PubMed ↗Publisher’s paper ↗

Citation

Unger, Jennifer B; Soto, Daniel W; Leventhal, Adam. (2016). E-cigarette use and subsequent cigarette and marijuana use among Hispanic young adults.. Drug and alcohol dependence, 163, 261-4. https://doi.org/10.1016/j.drugalcdep.2016.04.027