Featured Scientist: Melissa Blythe Harrell (she/hers), PhD MPH, UTHealth Houston, School of Public Health, Department of Epidemiology, Human Genetics, and Environmental Health

Hometown: Austin, TX
My Research: I am a tobacco scientist, with a focus on youth and young adult tobacco use.
Research Goals: I love doing research with the wonderful team of investigators that have gathered around me over the last two decades. I am hoping to make a return to India in the next five years, where my tobacco research originally began.
Career Goals: See Research Goals. I love simply doing good work with good people.
Hobbies: Yoga, reading, cooking, spending time with my dog Bugsy.
Favorite Thing About Science: “Creating” new avenues in the field of public health.
Scientist upbringing: I always thought I would be a physician but ended up in epidemiology instead. It’s been a fun ride, with a lot of work to keep me busy!
My Team: I typically serve as the “Principal Investigator” on my research projects, meaning that I lead the team to develop and implement the study. The colleagues on my team come from all over the globe, with lots of varied training and experience!
Field of Study: Behavioral Epidemiology
What is behavioral epidemiology? Behavioral epidemiology is the study of the behaviors of people and how this affects their health. It is related to the fields psychology and epidemiology.
Organism of Study:

Check Out My Original Paper: “E-cigarette-specific symptoms of nicotine dependence among Texas Adolescents”

Citation: Case, K. R., Mantey, D. S., Creamer, M. R., Harrell, M. B., Kelder, S. H., & Perry, C. L. (2018). E-cigarette-specific symptoms of nicotine dependence among Texas adolescents. Addictive behaviors, 84, 57-61.
Article Written by Sydney Chowdhury (she/her) Junior Biology Major, Elizabeth Heselton (she/her) Senior Biology Major, Genesis Alarcon (she/her) Senior Biology Major, Derrick Andreasen (he/him) Junior Biology Major, Erika Camarillo (she/her) Junior Biology Major, Texas Tech University. Student authors were enrolled in the Topics in Biology: Bringing Science to the Community through Service-Learning course.
Research At a Glance: Electronic cigarettes are the most-used tobacco product among teenagers. There is still little research about e-cigarette use in this group. In this study, the authors looked at e-cigarette use and symptoms of dependence in teenagers living in Texas. Dependence refers to being reliant on something. In the context of this research, it refers to someone who needs cigarettes and e-cigarettes and can’t stop using them. To conduct this study, the authors surveyed teenagers in 7th, 9th, and 11th, grade using the Texas Adolescent Tobacco and Marketing Surveillance System (TATAMS). TATAMS is a survey that measures tobacco use, factors associated with tobacco use, and exposure to tobacco marketing products. The authors used the survey responses to find teenagers who use e-cigarettes and to measure dependence. The authors found that teenagers who use more than one tobacco product were more likely to show symptoms of dependence. They also found that more exclusive e-cigarette users reported wanting to quit, compared to those who used more than one tobacco product. This research shows that teenage who use e-cigarettes can develop dependence. It is important to understand tobacco use among teenagers because it has negative impacts on the body and can worsen quality of life.
Highlights: An important part of this study was understanding tobacco use among teenagers. The authors used data from the TATAMS survey to identify two groups: teenagers, those who only used e-cigarettes and those who used more than one tobacco product. Teenagers who only used e-cigarettes were called “exclusive e-cigarette users”. Teenagers that used more than one tobacco product were called “dual users”. The authors used survey questions from the Hooked-on Nicotine Checklist to measure dependence on e-cigarettes. For example, one question included in this survey was, “Do you ever have a strong urge to use an e-cigarette, e-cigarette pen, or e-hookah?” A Chi-squared test can be used to compare the results of a study to those expected by chance. In this study, the authors used a Chi-squared test to see if there was a difference in symptoms of dependence between exclusive e-cigarette users and dual users. They also used this test to see if the desire to quit was different between the two groups.
The authors found differences between exclusive users and dual users. The authors found that all users had symptoms of irritability, anxiousness, and difficulty concentrating. Many teenagers also chose “strong urge to use” and “really need to use” when describing symptoms of dependance on the survey. These symptoms were found in all users. However, dual users were more likely to show symptoms of dependence on e-cigarettes (Figure 1).

The authors also compared dual users and exclusive users based on their attempts to quit and what percent of them that wanted to quit. It was found that exclusive users were more likely to want to quit and to attempt to quit when compared to dual users (Figure 2).

What My Science Looks Like: In this study, the authors used the TATAMS survey to measure tobacco use among teenagers. One hundred and thirty-two students described using e-cigarettes within 30 days of the survey. These students reported many symptoms of dependence (Figure 3). The authors found that 45% percent of the students wanted to quit and 38.7% had already attempted to quit. These results show that teenagers are experiencing the negative effects of e-cigarette use. Unfortunately, symptoms of dependence may stop students from quitting, even when it’s something that they want.

The Big Picture: Many teenagers view e-cigarettes as safer than other tobacco products. However, this study found evidence that teenagers who use e-cigarettes experience symptoms of dependence. Teenagers using e-cigarettes feel irritable, have less focus, and have appetite problems. They also experience more anxiety and depression. The findings of this research show how important it is to help teenagers quit smoking. The research also shows that teenagers who are experiencing symptoms of dependence are also less likely to quit. The findings suggest that it may be an important to intervene at high schools. Teenagers of this age may already be struggling with dependence. Finding ways to help high school students now may contribute to their health the future.
Decoding the Language:
Chi-Squared Test: The chi-squared test is a statistical test that can be used to test a hypothesis. This test is used to compare observed outcomes to expected outcomes of an experiment. The main purpose of this test is to ensure that the differences of these outcomes are not due to chance, but rather due to the variables that are being tested. In the context of this research, the chi-squared test was used to see if dual user and exclusive users had difference symptoms of dependence.
Dependence: Dependence refers to a reliance on a substance for help or to provide what one needs. This might be an addiction or reliance on something such as nicotine.
Electronic cigarette (E-cigarette): An e-cigarette is an electronic device that simulates tobacco smoking. It consists of a rechargeable battery and a cartridge or tank. Instead of smoke, the user inhales vapor. As such, using an e-cigarette is often called “vaping”.
Epidemiology: Epidemiology refers to the study of diseases and how they occur.
Hooked-on Nicotine Checklist: The Hooked-on Nicotine Checklist is a 10-question survey used to determine the onset and strength of tobacco dependence. The target population for this are adolescents between the ages of 12-15. Scoring is based on the number of positive responses. The number of positive responses reflects the degree of dependence. Questions that may be asked include: Have you ever tried to stop vaping, but couldn’t? Do you ever have strong cravings to vape? When you tried to stop vaping… (or, when you haven’t vaped for a while…) did you find it difficult to concentrate? These questions are used to place the participant on a scale of dependence for further evaluation.
Nicotine: Nicotine is an addictive chemical found in e-cigarette products. It is a drug that speeds up the messages from the brain to the body. It is in all tobacco products.
Texas Adolescent Tobacco and Marketing Surveillance System (TATAMS): TATAMS is a population-based study of adolescents in major metropolitan areas of Texas. It assesses tobacco product use, and exposure to marketing of tobacco products in adolescents every six months over a period of three years. It was designed to understand the diversity of tobacco products used by youth and the impact of tobacco product marketing on use.
Learn More:
A YouTube video produced by Crash Course Statistics about chi-square tests, how to do them, and why they are important
The website for Truth, a nonprofit organization that works to end nicotine use in adolescents. The website provides articles on tobacco products, helpful links to resources for information, quitting programs that include motivational texts and counseling, and general information about adolescent nicotine use.
An article from the Centers for Disease Control and Preventions (CDC) that provides facts and basic information of e-cigarette use among adolescents.
A YouTube video produced by the David Geffen School of Medicine at University of California – Los Angeles with a short overview of e-cigarette use. It discusses the creation and distribution of e-cigarettes and how they are harmful.
Synopsis edited by Rosario Marroquín-Flores, PhD 2022, Texas Tech University
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Meet the Authors
Elizabeth Heselton (she/her), Senior at Texas Tech University

Elizabeth was born and raised in Dallas, TX, and is pursuing a bachelor’s degree in Biology with minors in Chemistry and Forensic Science at Texas Tech University. After graduation, she will be attending the Texas Tech University Health Sciences Center to obtain her Masters in Molecular Pathology. Following her masters, she hopes to apply to PA school. In her free time, she enjoys watching movies, playing with her corgi, traveling, and spending time with friends.
Genesis Alarcon (she/her), Senior at Texas Tech University

Genesis was raised in Texas, and is currently pursuing a bachelors in Biology with a minor in Chemistry at Texas Tech University. After graduation she hopes to either get a master’s degree or continue researching to ultimately go to medical school. In her free time, she likes to crochet, play basketball, and spend time with friends.
Erika Camarillo (she/her), Junior at Texas Tech University

Erika Camarillo was born in Queens, New York and currently resides in Houston, Texas. She is a biology major with minors in health professions and chemistry at Texas Tech University. After graduation, she plans to pursue a master’s degree in Molecular Pathology. Erika wishes to attend PA school specializing in obstetrics and gynecology. In her free time, she likes to spend time with family and friends, go to the gym, and cook.
Derrick Andreasen (he/him), Junior at Texas Tech University

Derrick Andreasen was born and raised in the San Francisco, CA area. He now lives in Lubbock Texas and attends Texas Tech University where he is pursuing a bachelor’s degree in biology and a minor in environmental toxicology. After graduation he will pursue a master’s degree in environmental toxicology. When not studying, he enjoys taking care of his five pets, playing Dungeons and Dragons, and spending time in his garden.
Sydney Chowdhury (she/her), Junior at Texas Tech University

Sydney Chowdhury was born and raised in Kilgore, Texas. She is currently pursuing a bachelor’s in biology with minors in Chemistry and Health Professions at Texas Tech University. After graduation, she is intending to pursue a master’s degree and ultimately attend medical school. In her free time, she enjoys reading, knitting, and spending time with her friends and family.