Ramzi W. Nahhas, PhD

Community Health
Associate Professor, Community Health & Psychiatry
Res Park-Tech Center IV 200, 3123 Research Blvd, Dayton, OH 45420-4035

Dr. Nahhas is highly active in collaborative projects, utilizing modern statistical methods to analyze data from a wide range of biomedical research areas. These areas include childhood growth and development, obesity, cardiometabolic risk across the lifespan, illicit drug use, and psychiatry. This diversity stems from the applicability of his focal statistical expertise to a wide variety of biomedical questions. Dr. Nahhas’ specific methodological areas of expertise include longitudinal data analysis, in particular linear and non-linear mixed models, growth curve modeling, and the analysis of missing data.

Professional Positions:

  • 2014–present: Associate Professor, Department of Community Health, Department of Psychiatry, 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 Bible Translators, 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



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 QuarterlyIn press.

Kashou N, Dar I, Hasenstab K, Nahhas RW, Jadcherla S. Somatic stimulation causes fronto-parietal cortical changes in neonates: an fNIRS study.
Neurophotonics. In press.

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. In press.

Kashou N, Giacherio B, Nahhas RW, Jadcherla S. Hand grasping and finger tapping induced similar fNIRS cortical responses.
Neurophotonics. In press.

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 26183902. (link)

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 26183902. (link)

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, 2015, Epub ahead of print.
DOI 10.1002/ajmg.b.32334. PMID 26183902. (link)

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. (link)

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. (link)

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.
DOI:10.1111/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. (link)

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. PII: S0376-8716(13)00415-8. PMID 24210772. PMCID PMC3865109. (link)

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. (link)

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. (link)

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, 150:68-75.
DOI 10.1002/ajpa.22142. PMID 23283666. PMCID PMC3988703. (link)

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, 150:48-57.
DOI 10.1002/ajpa.22183. PMID 23283664. PMCID PMC3539213. (link)

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. (link)

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. (link)

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. (link)

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. (link)

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. (link)

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. (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. (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. (link)

Nahhas RW, Wolfe DA, Chen H. Ranked set sampling: cost and optimal set size.
Biometrics, 2002, 58(4):946-971.
PMID 12495151. (link)

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. [Erratum in: American Journal of Clinical Nutrition, 1999, 69(3):577]. (link)

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.
PMID 9329346. (link)

Professional Affiliations/Memberships: 

American Statistical Association

Is this you? Log in to update your profile.