Assessing the Overlap Between Marijuana and Tobacco Use in Adults: A Mixed Methods Approach Open Access

Schauer, Gillian Leigh (2015)

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Tobacco use is more prevalent among people using other substances, including illicit drugs. Data suggest an overlap between tobacco and marijuana, the most widely used federally illicit substance in the U.S. Given the well-documented harms from tobacco, co-occurring tobacco use is an important and concerning comorbidity of marijuana use. Existing research on this topic focuses largely on adolescents and young adults. Nationally representative data on the prevalence of and trends in co-use among adults are not available, and are needed to characterize the extent of the epidemic in light of changing marijuana policies. Additionally, although a number of theoretical reasons have been proposed to explain overlapping use of marijuana and tobacco, no qualitative studies have been conducted with adults to understand reasons for and patterns of co-use. Accordingly, this mixed methods research sought to quantify and characterize co-use of marijuana and tobacco in adults. Data for the quantitative component of this research came from the 378,459 adults age 18 years and older who responded to the 2003-2012 National Survey on Drug Use and Health, a nationally representative, household interview survey conducted annually. Data for the qualitative component were collected from Washington State residents aged 18-34 years who reported past month use of both tobacco and marijuana (n=48). Taken together, findings suggest that co-use increased among the U.S. adult population between 2003-2012, with increases occurring among those ages 26-34 and 50+ years. Among adult marijuana users, blunt use (cigar wrappers filled with marijuana) increased significantly between 2005-2012, while cigarettes use decreased. Qualitative findings suggest that adults aged 18-34 years report using marijuana in specific ways (e.g., sequentially, co-administered, as substitutes) and for different reasons (e.g., to enhance the high, ease cravings or addiction to nicotine, help cut back on use of one or both substances, or when use of one substances is not available, appropriate or allowed), with qualitative themes differing based on frequency of use. These data provide an epidemiologic foundation to justify ongoing studies to prevent and reduce co-occurring marijuana and tobacco use in adults. Qualitative findings on reasons for co-use provide possible avenues for future, theory-based interventions.

Table of Contents

CHAPTER 1: Introductory Literature Review 1

Marijuana Use 1

Marijuana use among U.S. adults 1

Changing risk perceptions about marijuana 2

Changing marijuana use policies 3

Marijuana products and modes of use 4

Increasing potency of marijuana 5

Marijuana abuse and dependence 6

Health effects and comorbidity due to marijuana use 8

Tobacco Use 11

Tobacco use among U.S. adults 11

Tobacco products and modes of use 12

Nicotine abuse and dependence 13

Health effects and comorbidity due to tobacco use 14

Co-Use of Marijuana and Tobacco 15

Tobacco use among marijuana users 15

Marijuana use among tobacco users 16

Relationship with alcohol 17

Overlapping products and modes of use 17

Health effects of marijuana and tobacco co-use 19

Sociodemographic correlates of co-use 21

Reasons for Marijuana and Tobacco Co-Use 22

Shared mode of use 23

Physiologic effects 23

Shared environmental factors 24

Shared genetic factors 25

Limitations of Previous Research 26

Proposed Mixed-Methods Research 28

Quantitative studies 29

Qualitative study 30

Summary 31

References 33

CHAPTER 2: Trends in Patterns of Co-Use of Tobacco and Marijuana in Adults from 2003-2012

Abstract 61

Introduction 63

Methods 66

Results 69

Discussion 71

References 82

CHAPTER 3: Differences in Tobacco Product Use Among Past Month Adult Marijuana Users and Non-Users

Abstract 90

Introduction 92

Methods 95

Results 99

Discussion 102

References 112

CHAPTER 4: Differences in the Relationship of Marijuana and Tobacco by Frequency of Use: A Qualitative Study with Adults Aged 18-34 years

Abstract 120

Introduction 122

Methods 124

Results 127

Discussion 136

References 142

CHAPTER 5: Summary and Conclusions 147

References 156

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