About

Dr. David S. Timberlake is an Associate Professor in the Department of Population Health and Disease Prevention at UC Irvine, with additional appointments in the School of Medicine's Epidemiology program. He holds a Ph.D. from the University of California, San Diego. His research primarily focuses on genetic epidemiology and the epidemiology of substance use, including tobacco, alcohol, and other substances of abuse. Dr. Timberlake has dedicated his work to understanding the biological mechanisms underlying drug abuse, particularly through the study of the dopamine-reward system and candidate gene polymorphisms. His research addresses three main areas: the associations between drug use and genetic variations in the dopamine pathway, environmental factors that influence genetic predispositions to substance use, and the measurement and predictors of nicotine dependence. He utilizes national survey data such as Add Health, NSDUH, and NESARC to explore adolescent substance use behaviors, transitions in tobacco and cannabis use, and issues related to nicotine dependence and smoking cessation. Dr. Timberlake's work contributes to the broader understanding of the genetic and epidemiologic factors influencing substance use and dependence.

Research topics

• Medicine
• Environmental health
• Sociology
• Psychology
• Clinical psychology
• Economic growth
• Psychiatry
• Geography
• Gerontology
• Demography
• Economics
• Advertising
• Business
• Social psychology
• Neuroscience

Selected publications

• Demographic subgroups of adult lifetime users of oral nicotine pouches in the United States

  Preventive Medicine · 2026-03-27

  article1st authorCorresponding
  PublisherDOI

• Mini-review: Harm reduction strategies among people who intentionally use fentanyl

  Addictive Behaviors Reports · 2025-05-24 · 2 citations

  articleOpen accessSenior author

  Background: Most published studies aimed at curtailing the morbidity and mortality associated with the current U.S. opioid epidemic have focused on unintentional exposure to fentanyl through heroin, cocaine, and other substances. Yet, there is mounting evidence that the intentional use of fentanyl is a key contributor to the current epidemic. In this mini-review we will discuss the harm reduction methods employed by people who intentionally use fentanyl (PWIUF) from a handful of articles found through PubMed that included PWIUF that were published between January 2013 to January 2024. Results: The perceived harm reduction strategies included co-use of stimulants, dose reduction, buying from a trusted dealer, drug checking, conducting a test shot, carrying naloxone, using fentanyl with others, and switching from injection to another route of administration (e.g., smoking). Some of these harm reduction strategies are frequently used by persons who inject heroin but future research on the efficacy of these harm reduction strategies for fentanyl use is warranted. It is important to note that co-use of stimulants has been associated with an increase in overdose. Conclusion: Future research is needed to understand intentional fentanyl use, perceived harm reduction strategies and the efficacy of these strategies with the advent of stronger opioids. Future research about PWIUF should consider novel study designs such as the ecological momentary assessment for more granular observation of the use of harm reduction strategies.

  PublisherDOI

• Did the United States smokeless tobacco industry use cigarette industry strategies to sponsor and manipulate research?

  Addiction · 2025-03-15

  articleOpen access1st authorCorresponding

  BACKGROUND AND AIM: The cigarette industry in the United States (US) laid the foundation for sponsoring research to improve public relations and defend against product liability cases. Fewer threats of litigation facing the US smokeless tobacco (SLT) industry may have contributed to the sponsorship of independent research on SLT use and health outcomes. This study aimed to determine whether the SLT industry used cigarette industry strategies to manipulate research on health risks. METHODS: Internal industry documents (e.g. letters, memos) from the 1970s through 1990s were accessed through the online Truth Tobacco Industry Documents Library at the University of California, San Francisco. A framework of tobacco industry strategies and criteria for evaluating sponsored research formed the basis for categorizing and synthesizing documents identified via snowball sampling (n = 177). Summaries of awarded projects in annual reports of the Smokeless Tobacco Research Council (STRC) were coded for content (n = 189, 1982-1997). RESULTS: Guided by legal counsel, the SLT industry sponsored research to support its interest group position; advocated against research on tobacco-specific carcinogens such as N-nitrosonornicotine (NNN); heavily criticized a case-control study on oropharyngeal cancer; and relied on a cadre of grantees and STRC leadership to testify against SLT restrictions. The STRC awarded a high proportion of projects on nicotine (78/189), including use for therapy (e.g. Tourette's syndrome), but underfunded epidemiologic research (n = 3). However, the STRC awarded projects on extracts or constituents (e.g. NNN, n = 30) that may have implicated SLT's role in carcinogenesis. CONCLUSIONS: While the Smokeless Tobacco Research Council awarded some research that may have weakened the industry, the Council's imbalanced portfolio of projects and inextricable link to industry likely favored the interest group position. Thus, we cannot conclude that the smokeless tobacco industry sponsored research solely for scientific discovery. Greater independence of industry-sponsored research could be achieved by delegating scientific decision-making to scientists (not legal counsel), limiting governance to those unaffiliated with the industry sponsor and not relying on grantees to defend the interest group position.

  PublisherOA PDFDOI

• Assessing violation of local cannabis delivery bans prior to enactment of California’s Senate Bill 1186

  International Journal of Drug Policy · 2025-10-16

  article1st authorCorresponding
  PublisherDOI

• Local Cannabis Policy and Cannabis Use by California High School Students Before and After Statewide Retail Legalization

  Journal of Adolescent Health · 2025-10-10 · 1 citations

  articleOpen access
  PublisherOA PDFDOI

• Role of trade associations in managing conflict between US cigarette and smokeless tobacco industries

  Tobacco Control · 2025-11-25

  article1st authorCorresponding

  OBJECTIVE: The merging of US smokeless tobacco (SLT) and cigarette industries in the early 2000s was highly predictable based on cigarette manufacturers' long-standing interest in developing SLT products. Yet, conflicts preceding the merger have not been examined, thus, warranting an investigation of how trade associations managed industry relations. METHODS: Materials from the Truth Tobacco Industry Documents Library were searched using names of the two trade associations, the Tobacco Institute (TI) and Smokeless Tobacco Council (STC). Names of committees, US state legislation and influential personnel employed by TI, STC and tobacco manufacturers formed the basis for additional searches. A total of 290 internal documents from the 1980s and 1990s were analysed for content. RESULTS: The cigarette industry's power over the SLT industry dictated how trade associations managed relations. While STC depended on TI for legislative support, TI depended on STC to align with its policy positions. Otherwise, any unresolved difference, notably the younger minimum age for sampling SLT, could lead US state legislators to enact indiscriminate policy affecting SLT and cigarettes (ie, complete sampling ban). Policy differences at the state level created a greater rift between trade associations than more consequential issues such as marketing SLT as a cigarette alternative. CONCLUSION: TI's quest for STC to align with its policy positions was intended to minimise restrictive measures on cigarettes, akin to transnational tobacco companies' acquisition of e-cigarette companies to influence tobacco control policy. Based on recent events, acquisitions of non-cigarette tobacco companies may be scrutinised by the US Federal Trade Commission.

  PublisherDOI

• Corporate Strategies to Market PAX Vaporizers for Cannabis Use Under Federal Restrictions in the United States

  Substance Use & Misuse · 2025-10-21

  article1st authorCorresponding

  OBJECTIVE: Legal restrictions have limited the overt marketing of cannabis and associated paraphernalia in the United States. This study assessed how one company, PAX Labs, marketed its devices for vaporizing cannabis while abiding by U.S. federal law on drug paraphernalia. METHODS: the JUUL Labs Collection at University of California, San Francisco. An initial Boolean query of the collection followed by snowball sampling yielded 421 informative documents for a content analysis. Two additional sources, archived PAX webpages and political/lobbying expenditure reports, were analyzed to triangulate findings on messaging and legislative support, respectively. RESULTS: The company first marketed PAX devices for vaporizing tobacco, transitioned to marketing use for an unnamed plant material, and then promoted cannabis vaporization as U.S. state cannabis laws became more liberalized. PAX Labs carefully navigated marketing restrictions on drug paraphernalia through use of ambiguous messaging (i.e., "plant agnostic") and recruitment of cannabis-related third-party affiliates as a means of distancing the company from cannabis promotion. Although PAX Labs did not publicly or financially support U.S. state cannabis ballot measures in 2016, the company proposed to sponsor events facilitating public conversations on cannabis legalization. CONCLUSION: Strategies used by PAX Labs pose challenges for government agencies that do not have purview to regulate cannabis vaporizers that are vaguely marketed. Yet, government agencies can better assess adherence to federal law on drug paraphernalia by carefully monitoring vaporizer companies' use of ambiguous messaging, affiliate marketing, and cannabis forum sponsorship.

  PublisherDOI

• A Qualitative Assessment of Blunt Smokers' Perceptions and Receptivity to Non-Tobacco Blunt Wraps

  Journal of Studies on Alcohol and Drugs · 2024-04-22 · 1 citations

  articleSenior author

  OBJECTIVE: The recent debut of the non-tobacco blunt wrap (N-TBW) for smoking cannabis has received little attention from the tobacco control community. The present study is intended to assess blunt smokers' perceptions and receptivity to N-TBWs, which are being marketed as an alternative to cigarillos and other tobacco products used for making blunts. METHOD: = 41) were recruited from social media platforms to participate in one of nine 2-hour focus groups held between October 2022 and May 2023. Six topics ranging from social aspects of blunt smoking to impediments to switching to N-TBWs were discussed. A domain analysis was used to uncover semantic relationships between a given variable (e.g., uneven burn rate) and outcome (e.g., not using N-TBWs). RESULTS: Blunt smokers conveyed interest in the N-TBWs because of health concerns about tobacco. Yet, the following three main barriers impede blunt smokers' use of N-TBWs: lack of awareness and accessibility of the N-TBW, familiarity with preparing and smoking a traditional blunt, and incomparability of the tobacco blunt wrap (e.g., cigarillo). The latter was the most formidable challenge because participants expressed several negative product features of N-TBWs (e.g., flimsy material) relative to cigarillos. CONCLUSIONS: The N-TBW is unlikely to displace the cigarillo in the near future. A more likely scenario is that blunt smokers will continue to use cigarillos with intermittent use of N-TBWs in situational settings. If this occurs, then blunt smokers will continue to be exposed to harmful tobacco products.

  PublisherDOI

• Establishing a standard measure of blunt and cigar use for U.S. national surveys

  Addictive Behaviors · 2024-09-06 · 2 citations

  article1st authorCorresponding
  PublisherDOI

• Age-Gating and Marketing Differences Between Storefront and Non-Storefront Cannabis Retailers

  Cannabis · 2024-05-29 · 1 citations

  articleOpen accessSenior author

  Objective: The study investigated whether California storefront and non-storefront cannabis retailers are adhering to online age-gating requirements and whether differences in website marketing practices exist. Methods: Websites of 134 storefront and 115 non-storefront licensed retailers were randomly selected. Bivariate associations were tested between retailer type and website marketing, age-gating methods, and presence of age-gating at various purchase stages. Results: Among the 200 (80.3%) websites with age-gating when entering, 182 (91%) employed an ineffective method where users click either “Yes” or “No” to confirm their age. Moreover, 49 (19.68%) websites lacked age-gating when entering. Amongst those requiring photo identification during checkout (n = 100, 40.16%), 97% allowed users to proceed after uploading an irrelevant image. Significantly more storefront retailers employed combined age-gating at entry, mandatory account registration, and age-gating during checkout than non-storefront retailers (X2 (1, N = 249) = 7.69, p < .01). Retailer websites frequently displayed “clean” labels (n = 200, 80.32%), followed by positive state claims (n = 198, 79.52%), physical health claims (n = 166, 66.67%), and mental health claims (n = 146, 58.63%). Significantly more storefront retailers displayed physical health claims (X2 (1, N = 249) = 7.52, p < .01) and health warnings than non-storefront retailers (X2 (1, N = 249) = 4.13, p = .04). Conclusions: Most cannabis retailers comply with age-gating requirements; however, methods employed are easily circumvented. Youths’ easy and unrestricted access to cannabis retailer websites may increase positive attitudes about cannabis and encourage use.

  PublisherOA PDFDOI

Recent grants

• NIH Grant R03DA027950

  NIH · $134k · 2015

Frequent coauthors

• Daniel T. O’Connor

  University of California, Davis

  26 shared

• Brett C. Haberstick

  University of Colorado Boulder

  23 shared

• Arja Rimpelä

  Tampere University Hospital

  22 shared

• Christian J. Hopfer

  22 shared

• John K. Hewitt

  18 shared

• Elizabeth A. Roberts

  University of California, San Diego

  16 shared

• Lisa U. Yoneda

  University of California, San Diego

  16 shared

• Fred A. Wright

  16 shared

Labs

• UC Irvine - Faculty Profile SystemPI

Education

• Ph.D.

  University of California, San Diego