Archives of Sexual Behavior

, Volume 46, Issue 2, pp 419–432 | Cite as

Number of Sexual Partners and Relationship Status Are Associated With Unprotected Sex Across Emerging Adulthood

  • James R. AshenhurstEmail author
  • Emily R. Wilhite
  • K. Paige Harden
  • Kim Fromme
Original Paper


Sex with multiple partners, consecutively or concurrently, is a risk factor for contracting sexually transmitted infections (STIs) as multiple partner–partner contacts present increased opportunity for transmission. It is unclear, however, if individuals who tend to have more partners also use protection less reliably than those with sexual histories of fewer partners. Longitudinal data can elucidate whether an individual shows a consistent pattern of sex with multiple partners. We used latent class growth analyses to examine emerging adult survey data (N = 2244) spanning 10 waves of assessment across 6 years. We identified three trajectory classes described with respect to number of partners as (a) Multiple, (b) Single, and (c) Rare. Trajectory group, relationship status, and their interactions were tested as predictors of using protection against STIs and pregnancy at each wave. The Multiple Partners class had the greatest odds ratio of reporting sex without protection against STIs and pregnancy, followed by the Single and Rare classes. Exclusive relationship status was a risk factor for unprotected sex at earlier waves, but a protective factor at most later waves. There was no significant interaction between relationship status and trajectory class in predicting use of protection. The Multiple Partners class reported more permissive values on sex and an elevated proportion of homosexual behavior. This group overlaps with an already identified at-risk population, men who have sex with men. Potential mechanisms explaining the increased risk for sex without protection, including communication, risk assessment, and co-occurring risk behaviors are discussed as targets for intervention.


Unprotected sex Emerging adults Trajectory analysis Multiple sex partners Sexual risk behavior 



We would like to thank Elise Marino, Susan Kirtz, and Dr. Elliot Tucker-Drob for their assistance in the development of this manuscript.

Compliance with Ethical Standards

All listed authors contributed significantly to this article in terms of study design, analysis, and writing. All authors approved the final article. This research was supported by training Grant 5T32 AA7471-28 (Ashenhurst) and NIAAA RO1-AA013967 (Fromme).

Conflicts of interest

The authors declare no conflicts of interest pertaining to the data or analysis presented herein.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.

Supplementary material

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Supplementary material 5 (DOCX 89 kb)


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.Department of PsychologyThe University of Texas at AustinAustinUSA

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