Ramzi W. Nahhas, PhD

Population and Public Health Sci
Associate Professor, Population & Public Health; Associate Professor, Psychiatry
Res Park-Tech Center IV 200, 3123 Research Blvd, Dayton, OH 45420-4035

Department of Population and Public Health Sciences (formerly known as the Department of Community Health)

Dr. Nahhas is highly active in collaborative projects, utilizing modern statistical and epidemiological methods to analyze data from a wide range of biomedical research areas. These areas include public health, psychiatry, illicit drug use, childhood growth and development, obesity, and cardiometabolic risk across the lifespan. Specific methodological areas in which Dr. Nahhas’ has experience include longitudinal data analysis, in particular linear and general linear regression analyses, linear and non-linear mixed models, growth curve modeling, latent class analysis, and the analysis of missing data. Additionally, he serves as the resident biostatistician for WSU's Center for Interventions, Treatment, and Addictions Research and the Department of Psychiatry, engaged in statistical collaboration and training of residents and fellows.

Professional Positions:

  • 2014-present: Associate Professor, Department of Population and Public Health Sciences (Primary Appointment), Department of Psychiatry (Secondary Appointment), Boonshoft School of Medicine, Wright State University, Dayton, OH
  • 2009–2014: Assistant Professor, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH
  • 2008–2009: Research Assistant Professor, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH
  • 2007–2008: Sr. Biostatistician, Lifespan Health Research Center, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH
  • 2006–2007: Language Survey Coordinator, Department of Linguistics, Payap University and SIL International, Chiang Mai, Thailand
  • 2004–2006: Language Survey Specialist, Department of Linguistics, Payap University and SIL International, Chiang Mai, Thailand
  • 2002: Statistics Instructor, Graduate Institute of Applied Linguistics, Dallas, TX
  • 2000–2007: Language Surveyor, Wycliffe, Dallas, TX and Chiang Mai, Thailand (seconded to SIL International 2003-2007)
  • 1999–2000: Research Scientist, Battelle, Columbus, OH
Education History: 
  • 1999, Ph.D., Biostatistics, The Ohio State University, Columbus
  • 1995, M.S., Statistics, The Ohio State University, Columbus
  • 1993, B.S., Mathematics, The Ohio State University, Columbus


  • PPH 7920-01: Applied Statistics Practicum, Master of Public Health program, Boonshoft School of Medicine (2016-18) [Course developer & instructor]
  • Introduction to Research, Department of Psychiatry, Boonshoft School of Medicine (2015-18) [Course development team member, Co-instructor]
  • PPH 7920-01: Public Health Epidemiology II, Master of Public Health program, Boonshoft School of Medicine (2015-17) [Co-course developer and Co-instructor]
  • PPH 7150-01: Applied Epidemiology (Chronic Disease Epidemiology), Master of Public Health program, Boonshoft School of Medicine (2017) [Co-course developer]
  • Guest lecture: Logistic Regression. CMH6100-01: Biostatistics for Health Professionals, Master of Public Health program, Boonshoft School of Medicine (2015)
  • Guest lecture: Sample size calculation methods using PASS. CMH 791-05: Advanced Statistical and Epidemiology Methods using SPSS, Master of Public Health program, Boonshoft School of Medicine (2012)
  • AL733: Language Development Methods. Payap University, Graduate Studies Center, Department of Linguistics, Chiang Mai, Thailand (2006) [Course developer & instructor]
  • LD5342: Statistical Methods, Graduate Institute of Applied Linguistics, Dallas, TX (2002)
  • Member, Editorial Board, American Journal of Human Biology (since 2016)
  • Section Councilor, Epidemiology Section, American Public Health Association (2017-2020)
  • Boonshoft School of Medicine Representative, WSU Faculty Senate Executive Committee (2017-2018)
  • Senator, WSU Faculty Senate (2017-2019)
  • Research Committee, Boonshoft School of Medicine (2015-2019)



Published articles with a PMID: My bibliography at My NCBI Collections

All articles (accepted, in press, and published):

Khalil N, Wallace KD, Tahtamooni OT, Rogers NL, Nahhas RW. Association of secondhand smoke with increased sagittal abdominal diameter in the US population: NHANES 2011-2012.
Environmental Disease. 2018, In press.

Khalil N, Kaur B, Lawson A, Ebert J, Nahhas RW. Secondhand smoke exposure is associated with Autism Spectrum Disorder in U.S. males but not in females: results from the National Survey on Children's Health.
Environmental Disease. 2018, 3(1):8-17.
DOI 10.4103/ed.ed_2_18.

Daniulaityte R, Zatreh M, Lamy FR, Nahhas RW, Martins SS, Sheth A, Carlson RG. A Twitter-based survey on marijuana concentrate use.
Drug and Alcohol Dependence. 2018, 187:155-159.
DOI 10.1016/j.drugalcdep.2018.02.033. PMID 29669296. PMCID PMC5959780 [Available on 2019-06-01].

Guina J, Nguyen M, Farnsworth S, Nahhas RW. PTSD symptom severity, but not trauma type, predicts mental health help-seeking in the military.
Journal of Psychiatric Practice. 2018, In press

Lamy FR, Daniulaityte R, Zatreh M, Nahhas RW, Sheth A, Martins SS, Boyer EW, Carlson RG. "You got to love rosin: Solventless dabs, pure, clean, natural medicine." Exploring Twitter data on emerging trends in Rosin Tech marijuana concentrates.
Drug and Alcohol Dependence. 2018, 183: 248–252.
DOI 10.1016/j.drugalcdep.2017.10.039. PMID 29306816. PMCID PMC5803369 [Available on 2019-02-01].

Khalil N, Honda M, Ebert J, Lee M, Koskela A, Hangartner T, Nahhas RW, Kannan K. Perfluoroalkyl substances, bone density, and cardio-metabolic risk factors in obese 8-12 year old children: a pilot study.
Environmental Research. 2018, 160:314-321.
DOI 10.1016/j.envres.2017.10.014. PMID 29040951.

Guina J, Nahhas RW, Sutton P, Farnsworth S. The influence of trauma type and timing on PTSD symptomology.
Journal of Nervous and Mental Disease. 2018, 206(1):72-76.
DOI 10.1097/NMD.0000000000000730. PMID 29271827.

Gspandl S, Peirson R, Nahhas RW, Skale T, Lehrer D. Comparing Global Assessment of Functioning (GAF) and World Health Organization Disability Assessment Schedule (WHODAS) 2.0 in schizophrenia.
Psychiatry Research. 2018, 259:251-253.
DOI 10.1016/j.psychres.2017.10.033. PMID 29091824.

Daniulaityte R, Lamy FR, Smith GA, Nahhas RW, Carlson RG, Thirunarayan K, Martins SS, Boyer EW, Sheth A. “Retweet to pass the blunt”: Analyzing geographic and content features of cannabis-related tweeting activity across the U.S.
Journal on Studies of Alcohol and Drugs. 2017, 78(6):910-915.
DOI 10.15288/jsad.2017.78.910. PMID 29087826. PMCID PMC5668996 [Available on 2018-11-01].

Guina J, Nahhas RW, Mata N, Farnsworth S. Which Posttraumatic Stress Disorder symptoms, trauma types, and substances correlate with suicide attempts in trauma survivors?
Primary Care Companion for CNS Disorders. 2017, 19(5).
PII: 17m02177. DOI 10.4088/PCC.17m02177. PMID 29099549.

Daniulaityte R, Lamy FR, Barrat M, Nahhas RW, Martins SS, Boyer EW, Sheth A, Carlson RG. Characterizing marijuana concentrate users: a web-based survey.
Drug and Alcohol Dependence. 2017, 178:399-407.
DOI 10.1016/j.drugalcdep.2017.05.034. PMID 28704769. PMCID PMC5567791.

Guina J, Nahhas RW, Welton RS. No role for benzodiazepines in posttraumatic stress disorder until supported by evidence.
Australasian Psychiatry. 2017, 25(4):415-416.
DOI 10.1177/1039856217711061. PMID 28747110.

Lamy FR, Daniulaityte R, Nahhas RW, Barratt MJ, Sheth A, Smith GA, Martins SS, Boyer EW, Carlson RG. Increase in synthetic cannabinoids-related harms: results from a longitudinal web-based content analysis.
International Journal of Drug Policy. 2017, 44:121-129.
DOI 10.1016/j.drugpo.2017.05.007. PMID 28578250. PMCID PMC5545681.

Green CL, Nahhas RW, Scoglio AA, Elman I. Post-traumatic stress symptoms in pathological gambling: potential evidence of anti-reward processes.
Journal of Behavioral Addictions. 2017, 6(1):98-101.
DOI 10.1556/2006.6.2017.006. PMID 28274137. PMCID PMC5572998.

Zeola MP, Guina J, Nahhas RW. Mental health referrals reduce recidivism in first-time juvenile offenders, but how do we determine who is referred?
Psychiatric Quarterly. 2017, 88(1):167-183.
DOI 10.1007/s11126-016-9445-z. PMID 27241528.

Kashou N, Dar I, Hasenstab K, Nahhas RW, Jadcherla S. Somatic stimulation causes frontoparietal cortical changes in neonates: a functional near-infrared spectroscopy study.
Neurophotonics. 2017, 4(1):011004.
DOI 10.1117/1.NPh.4.1.011004. PMID 27570791. PMCID PMC4981749.

Guina J, Nahhas RW, Kawalec K, Farnsworth S. Are gender differences in DSM-5 PTSD symptomatology explained by sexual trauma?
Journal of Interpersonal Violence. 2016, 1-28.
DOI 10.1177/0886260516677290. PMID 27827321.

Guina J, Nahhas RW, Goldberg AJ, Farnsworth S. PTSD symptom severities, interpersonal traumas and benzodiazepines are associated with substance-related problems in trauma patients.
Journal of Clinical Medicine. 2016, 5(8):70.
DOI 10.3390/jcm5080070. PMID 27517964. PMCID PMC4999790.

Lamy FR, Daniulaityte R, Sheth A, Nahhas RW, Martins SS, Boyer EW, Carlson RG. Those edibles hit hard: Exploration of Twitter data on cannabis edibles in the U.S.
Drug and Alcohol Dependence, 2016, 164:64-70.
DOI 10.1016/j.drugalcdep.2016.04.029. PMID 27185160. PMCID PMC4893972.

Kashou N, Giacherio B, Nahhas RW, Jadcherla S. Hand-grasping and finger tapping induced similar functional near-infrared spectroscopy cortical responses.
Neurophotonics, 2016, 3(2):025006.
DOI 10.1117/1.NPh.3.2.025006. PMID 27335888. PMCID PMC4909125.

Carlson RG, Nahhas RW, Martins SS, Daniulaityte R. Predictors of transition to heroin use among non-opioid dependent illicit pharmaceutical opioid users: a natural history study.
Drug and Alcohol Dependence, 2016, 160:127-134.
DOI 10.1016/j.drugalcdep.2015.12.026. PMID 26785634. PMCID PMC4767561.

Lehrer DS, Pato MT, Nahhas RW, Miller BJ, Malaspina D, Sobell JL, Buckley PF, Pato CN. Paternal age effect: Replication in schizophrenia with intriguing dissociation between bipolar with and without psychosis.
American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 2016, 171(4):495-505.
DOI 10.1002/ajmg.b.32334. PMID 26183902.

Daniulaityte R, Nahhas RW, Wijeratne S, Carlson RG, Lamy FR, Martins SS, Boyer EW, Smith GA, Sheth A. “Time for dabs”: Analyzing Twitter data on marijuana concentrates across the U.S.
Drug and Alcohol Dependence, 2015, 155:307-311.
DOI 10.1016/j.drugalcdep.2015.07.1199. PMID 26338481. PMCID PMC4581982.

Guina J, Rossetter SR, DeRhodes BJ, Nahhas RW, Welton RS. Benzodiazepines for PTSD: A systematic review and meta-analysis.
Journal of Psychiatric Practice, 2015, 21(4):281-303.
DOI 10.1097/PRA.0000000000000091. PMID 26164054.

Duren DL, Nahhas RW, Sherwood RJ. Do secular trends in skeletal maturity occur equally in both sexes?
Clinical Orthopaedics and Related Research, 2015, 473(8):2559-2567.
DOI 10.1007/s11999-015-4213-1. PMID 25716212. PMCID PMC4488188.

von Hippel PT, Nahhas RW, Czerwinski SA. How much do children’s body mass indices change over intervals of 6-12 months? Statistics from before and during the obesity epidemic.
Pediatric Obesity, 2015, 10(6):468-475.
DOI10.1111/ijpo.12008. PMID 25704952.

Nahhas RW, Valiathan M, Sherwood RJ. Variation in onset, duration, intensity, and direction of adolescent growth in the mandible, maxilla, and cranial base: The Fels Longitudinal Study.
The Anatomical Record, 2014, 297(7):1195–1207.
DOI 10.1002/ar.22918. PMID 24737730. PMCID PMC4103980.

Carlson RG, Nahhas RW, Daniulaityte R, Martins SS, Li L, Falck RS. Latent class analysis of non-opioid dependent illegal pharmaceutical opioid users in Ohio.
Drug and Alcohol Dependence, 2014, 134:259-266.
DOI 10.1016/j.drugalcdep.2013.10.004. PMID 24210772. PMCID PMC3865109.

Nahhas RW, Sherwood RJ, Chumlea WC, Duren DL. An update of the statistical methods underlying the FELS method of skeletal maturity assessment.
Annals of Human Biology, 2013, 40(6):505-514.
DOI 10.3109/03014460.2013.806591. PMID 23992229. PMCID PMC4013782.

von Hippel PT, Nahhas RW. Extending the history of child obesity in the United States: The Fels Longitudinal Study, birth years 1930 to 1993.
Obesity, 2013, 21(10):2153-2156.
DOI 10.1002/oby.20395. PMID 23512972. PMCID PMC3695078.

Nahhas RW, Sherwood RJ, Chumlea WC, Towne B, Duren DL. Predicting the timing of maturational spurts in skeletal age.
American Journal of Physical Anthropology, 2013, 150(1):68-75.
DOI 10.1002/ajpa.22142. PMID 23283666. PMCID PMC3988703.

Duren DL, Šešelj M, Froehle AW, Nahhas RW, Sherwood RJ. Skeletal growth and the changing genetic landscape during childhood and adulthood.
American Journal of Physical Anthropology, 2013, 150(1):48-57.
DOI 10.1002/ajpa.22183. PMID 23283664. PMCID PMC3539213.

Froehle AW, Nahhas RW, Sherwood RJ, Duren DL. Age-related changes in spatiotemporal characteristics of gait accompany ongoing lower limb linear growth in late childhood and early adolescence.
Gait and Posture, 2013, 38(1):14-19.
DOI 10.1016/j.gaitpost.2012.10.005. PMID 23159678. PMCID PMC3580126.

Linabery AM, Nahhas RW, Johnson W, Choh AC, Towne B, Odegaard AO, Czerwinski SA, Demerath EW. Stronger influence of maternal than paternal obesity on infant and early childhood body mass index: The Fels Longitudinal Study.
Pediatric Obesity, 2013, 8(3):159-169.
DOI 10.1111/j.2047-6310.2012.00100.x. PMID 23042783. PMCID PMC3765070.

Odegaard AO, Choh AC, Nahhas RW, Towne B, Czerwinski SA, Demerath EW. Systematic examination of infant size and growth metrics as risk factors for overweight in young adulthood.
PLOS ONE, 2013, 8(6):e66994.
DOI 10.1371/journal.pone.0066994. PMID 23818973. PMCID PMC3688577.

Šešelj M, Nahhas RW, Sherwood RJ, Chumlea WC, Towne B, Duren DL. The influence of age at menarche on cross-sectional geometry of bone in young adulthood. 
Bone, 2012, 51(1):38-45.
DOI 10.1016/j.bone.2012.03.030. PMID 22513271. PMCID PMC3584571.

Falck RS, Nahhas, RW, Li, L, Carlson RG. Surveying teens in school to assess the prevalence of problematic drug use.
Journal of School Health, 2012, 82(5):217-224.
DOI 10.1111/j.1746-1561.2012.00690.x. PMID 22494092.

Daniulaityte R, Falck RS, Li L, Nahhas RW, Carlson RG. Respondent-driven sampling to recruit young adult non-medical users of pharmaceutical opioids: problems and solutions.
Drug and Alcohol Dependence, 2012, 121(1-2):23-29.
DOI 10.1016/j.drugalcdep.2011.08.005. PMID 21885213. PMCID PMC3256264.

Williams KD, Nahhas RW, Cottom CR, Lawrence S, Subedi J, Jha B, Czerwinski SA, Blangero J, Williams-Blangero S, Towne B. Evaluation of qualitative methods for phenotyping brachymesophalangia – V from radiographs of children.
American Journal of Human Biology, 2012, 24(1):68-73.
DOI 10.1002/ajhb.22205. PMID 22131202. PMCID PMC3457917.

Choh AC, Curran JE, Odegaard AO, Nahhas RW, Czerwinski SA, Blangero J, Towne B, Demerath EW. Differences in the heritability of growth and growth velocity during infancy and associations with FTO variants.
Obesity, 2011, 19(9):1847-1854.
DOI 10.1038/oby.2011.175. PMID 21720422. PMCID PMC4013792.

Choh AC, Nahhas RW, Lee M, Choi YS, Chumlea WC, Duren DL, Sherwood RJ, Towne B, Siervogel RM, Demerath EW, Czerwinski SA. Secular trends in blood pressure during early to middle adulthood: The Fels Longitudinal Study.
Journal of Hypertension, 2011, 29(5):838-845.
DOI 10.1097/HJH.0b013e328344da30. PMID 21430562. PMCID PMC3988666.

Lee M, Nahhas RW, Choh AC, Demerath EW, Duren DL, Chumlea WC, Sherwood RJ, Towne B, Siervogel RM, Czerwinski SA. Longitudinal changes in calcaneal quantitative ultrasound measures during childhood.
Osteoporosis International, 2011, 22(8):2295-2305.
DOI 10.1007/s00198-010-1458-0. PMID 20976593. PMCID PMC3988661.

Sherwood, RJ, Duren DL, Mahaney MC, Blangero J, Dyer TD, Cole SA, Czerwinski SA, Chumlea WC, Siervogel RM, Choh AC, Nahhas RW, Lee M, Towne B. A genome-wide linkage scan for quantitative trait loci influencing the craniofacial complex in humans (Homo sapiens sapiens).
The Anatomical Record, 2011, 294(4):664-675.
DOI 10.1002/ar.21337. PMID 21328561. PMCID PMC3091483.

Nahhas RW. Sociolinguistic survey of Lawa in Thailand.
SIL Electronic Survey Reports 2011-044. SIL: Dallas, TX. (link)

Nahhas RW, Choh AC, Lee M, Chumlea WC, Duren DL, Siervogel RM, Sherwood RJ, Towne B, Czerwinski SA. Bayesian longitudinal plateau model of adult grip strength.
American Journal of Human Biology, 2010, 22(5):648–656.
DOI 10.1002/ajhb.21057. PMID 20737612. PMCID PMC3988672.

Tehan TM, Nahhas RW. Mpi present and future: Reversing language shift.
Mon-Khmer Studies Journal, 2009, 38:87-104. (link)

Towne B, Williams KD, Blangero J, Czerwinski SA, Demerath EW, Nahhas RW, Dyer TD, Cole SA, Lee M, Choh AC, Duren DL, Sherwood RJ, Chumlea WC, Siervogel RM. Presentation, heritability, and genome-wide linkage analysis of the mid-childhood growth spurt in healthy children from the Fels Longitudinal Study.
Human Biology, 2008, 80(6):623-636.
DOI 10.3378/1534-6617-80.6.623. PMID 19728540. PMCID PMC2801436.

Nahhas RW. Sociolinguistic survey of Mpi in Thailand.
SIL Electronic Survey Reports 2007-016. SIL: Dallas, TX. (link)

Nahhas RW, Wolfe DA, Chen H. Ranked set sampling: ranking error models and estimation of visual judgment error variance.
Biometrical Journal, 2004, 46(2):255-263.
DOI 10.1002/bimj.200210021.

Nahhas RW, Wolfe DA, Chen H. Ranked set sampling: cost and optimal set size.
Biometrics, 2002, 58(4):964-971.
DOI: 10.1111/j.0006-341X.2002.00964.x. PMID 12495151.

Lanphear BP, Kahn RS, Berger O, Auinger P, Bortnick SM, Nahhas RW. Contribution of residential exposures to asthma in US children and adolescents.
Pediatrics, 2001, 107(6):E98.
PMID 11389296.

Ilich-Ernst JZ, McKenna AA, Badenhop NE, Clairmont AC, Andon MB, Nahhas RW, Goel P, Matkovic V. Iron status, menarche, and calcium supplementation in adolescent girls.
American Journal of Clinical Nutrition, 1998, 68(4):880-887.
PMID 9771866. (link) [Erratum in: American Journal of Clinical Nutrition, 1999, 69(3):577a-577].

Matkovic V, Ilich JZ, Skugor M, Badenhop NE, Goel P, Clairmont A, Klisovic D, Nahhas RW, Landoll JD. Leptin is inversely related to age at menarche in human females.
Journal of Clinical Endocrinology and Metabolism, 1997, 82(10):3239-3245.
DOI 10.1210/jcem.82.10.4280. PMID 9329346.

Professional Affiliations/Memberships: 
  • American Public Health Association
  • American Statistical Association
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