Early-life experiences and family relationship quality and investment lay the foundation for significant relationships throughout the lifespan (Belsky et al., 1991; Fraley & Roisman, 2015). These experiences culminate to create the psychological landscape in which individuals learn to navigate later social relationships (Ellis et al., 2009). Based on these experiences, individuals may either perceive their environments as safe and predictable or unsafe and unpredictable. Perceptions of environmental safety and predictability have been found to have resounding impacts on behavior—particularly those associated with growth, survival, and reproduction—which may potentially have implications on individual health and well-being (Del Giudice et al., 2011; Giskevicius et al., 2011; Lu & Chang, 2019). Although a great deal of past research has explored the associations between early-life experiences and/or family relationships with precocious sexual behaviors (Campbell & Udry, 1995; Chisholm et al., 1993; Ellis et al., 2012a, b; Simpson et al., 2012; Smith, 1997), little work has explored the associations between early-life experiences and/or family relationships with early cohabitation, defined by cohabitating with a romantic partner significantly earlier than same-aged peers. By extension, little work has explored the association between early cohabitation relationships and potential adjustment problems. The purpose of the present study was to explore how daily stress and family experiences were associated with the formation of early cohabitating romantic relationships, and, in turn, determine the emotional, behavioral, and physical health correlates of early cohabitation.

Life History Theories of Romantic Relationships

Life history theory explains how organisms allocate resources toward growth, survival, and reproduction based on environmental conditions (Charnov & Berrigan, 1993; Hill, 1993). According to this theory, individuals adaptively pattern their energy allocations based on early-life experiences and interaction with close kin, leading to subtly different life history strategies (LHS; Belsky et al., 1991; Ellis et al., 2009). One of the most salient early-life experiences that inform the development of LHS are the relationships an individual has with their parents (Del Giudice et al., 2011). Parent-youth relationship quality likely reflects perceptions of psychosocial opportunities and relative predictability of the environment—or lack thereof.

In Western cultures, like the United States, experiencing stable, high-investment parental relationships in early life is associated with stable romantic relationships in later development (slower LHS; Shulman & Connolly, 2013). Furthermore, past research has shown that these high-quality parent-youth relationships are a protective factor against risk-taking and antisocial behavior (Criss et al., 2021) and internalizing symptoms (Wood et al., 2024). On the other hand, experiencing unstable, low-investment, conflict-heavy parental relationships is linked to romantic relationships that occur earlier in development and are less stable in nature (faster LHS; Belsky et al., 1991; Ellis et al., 2009; Del Giudice et al., 2011). These low-quality parent-youth relationships drive the perceptions that the environment is unstable and unpredictable, and individuals following faster LHS often engage in sexual activity with multiple partners and form relationships earlier to facilitate reproduction in an environment where the future is uncertain (Colich et al., 2020; Ellis et al., 2012a, b; Griskevicius et al., 2011).

An alternative explanation for faster LHS is that their primary motivation may not be seeking multiple partners, but, instead, securing stable emotional and material support through committed relationships (Dinh et al., 2022). In unpredictable environments, the urgency to secure a partner can lead to rapidly accelerating relationship timelines, potentially overlooking signs of incompatibility and resulting in unstable partnerships (Ellis et al., 2009; Belsky et al., 1991). The perceived risks of delaying commitment—such as reduced mating opportunities—further drive this behavior, leading to fast-paced progression in relationships. As a result, these individuals may experience multiple partners, not from a preference for short-term relationships, but from repeated attempts to establish stable, long-term support (Mell et al., 2018; Ellis et al., 2009).

Romantic Relationships in Emerging Adulthood

Recent research has yielded evidence that emerging adulthood is a distinct developmental and life history stage for humans (Hochberg & Konner, 2020). Emerging adulthood—the phase between adolescence and full economic independence—is characterized by relationship exploration and instability (Arnett, 2000). During this time, romantic relationships can serve as practice for intimacy, conflict resolution, and the development of life skills essential for long-term partnership success (Connolly & McIsaac, 2009; Tuval-Mashiach & Shulman, 2006). The romantic relationships entered into during emerging adulthood can be informed by the quality of family relationships in earlier development. For example, high-quality relationships with parents set the stage for stable romantic relationships in early adulthood (Dhariwal et al., 2009), but low-quality relationships with parents can disrupt the establishment of stable relationships later in adulthood (Seiffge-Krenke et al., 2010).

One developmental milestone that has seen some change in recent years is cohabitation with a romantic partner. Compared to previous decades, cohabitating with a romantic partner has become more common (Nugent & Daugherty, 2018). However, emerging adults with college education are likely to cohabitate with a romantic partner later than peers without a college education (Wiik, 2009; Nugent & Daugherty, (2018). Emerging adulthood has largely been attributed to recent demographic shifts where, in Western cultures, milestones attributed with maturity (e.g., cohabitation, marriage, parenthood) that historically occurred at the end of the second decade are now occurring at the end of the third decade (Arnett, 2004; Furstenberg, 2010; Payne, 2019; Settersten & Ray, 2010; Shulman & Connolly, 2013). Thus, in Western cultures, emerging adults in higher-education environments who cohabitate with a romantic partner may be, in a sense, out of step with their peers in that they are establishing and maintaining cohabitating relationship while at the same time gaining educational and occupational skills.

Past research has identified that, in the U.S., individuals who experience early cohabitation are typically White, rural, from the southern U.S., and from lower-class families with relatively low educational attainment (Uecker & Stokes, 2008). These environments are often characterized by unpredictability, low resource availability, and increased mortality and morbidity, all of which are associated with adopting a faster life history course (Griskevicius et al., 2011; Miller & Vasan, 2021). There may be trade-off patterns in the distribution of resources for competing life goals (e.g., invest in somatic growth through education vs. establishment of long-term relationships) that are specific to individuals under these conditions and prompt them to enter committed, cohabitating relationships earlier than others.

“Early” Cohabitation

Cohabitation during emerging adulthood presents a complex interplay of risks and benefits. Understanding these dynamics is crucial for comprehending how family relationships and support influence the formation and maintenance of romantic relationships and its subsequent impact on health and well-being. For example, regarding the benefits of early cohabitation, it offers shared financial resources and emotional support, which enhance stability and reduce living costs (Kamp Dush & Amato, 2005; Addo, 2017). This is particularly true for individuals lacking family support. Cohabiting partners can pool their incomes and share expenses to foster financial resilience (Britt-Lutter et al., 2018). Additionally, cohabitating partners can provide emotional support that can help buffer stress and improve mental well-being (Umberson & Montez, 2010). Yet, it is important to note that, to receive these benefits the quality of the relationship is crucial. Although entering cohabitation earlier in development to receive financial or social support may serve as an adaptive response to an unpredictable environment, individuals who enter early cohabitating relationships may ultimately be sacrificing relationship and partner quality. Specifically, although early cohabitation can provide immediate social and financial support, the adaptive pursuit of a highly committed partner quickly may lead to partnerships that are less stable and more conflict-prone. Thus, entering cohabitation may ultimately undermine the potential benefits by exacerbating stress leading to mental and physical health challenges (Apostolou et al., 2024; Ellis et al., 2009). Furthermore, there is evidence that the responsibilities and conflicts associated with cohabitation can be significant sources of stress (Ross et al., 1990). The daily demands of managing a household, often compounded by financial strain and limited emotional resources (daily stress), can exacerbate mental health challenges, such as anxiety and depression (Thompson & Prottas, 2006). In summary, cohabitating relationships that are characterized by high levels of conflict and low levels of support may exacerbate stress and negate these benefits (Whitton & Kuryluk, 2012).

Early cohabitation can also take a toll on physical health as cohabitation may lead to changes to their diet and physical activity patterns to match those of their partners. For example, a partner’s unhealthy eating habits or sedentary lifestyle can negatively impact one’s own health behaviors, contributing to weight gain (Burke et al., 2004; Perry et al., 2016) and decreased physical fitness (Gordon-Larsen et al., 2004; Jackson et al., 2015; Pauly et al., 2020). These physical changes may further strain the relationship, leading to additional daily stress and dissatisfaction.

Moreover, emerging adults who cohabitate may find themselves isolated from their peer group, missing out on critical social interactions that are essential for personal growth and network building, especially during emerging adulthood when connections to families of origin may have diminished (Arnett, 2000). This isolation can lead to missed educational opportunities or career advancements, as the demands of cohabitation take precedence over personal ambitions (Stafford et al., 1977; Wong, 2017). The combination of social isolation and missed career or educational prospects can have major implications for mental health, contributing to higher rates of depression and anxiety (Brown, 2000). Research has found that individuals in stressful or unstable cohabiting relationships report higher levels of suicidal ideation and attempts compared to their non-cohabiting peers (Simon & Barrett, 2010).

Current Study

Life history theory argues that family relationships can have resounding influences on behaviors associated with growth, survival, and reproduction (Gluckman et al., 2007; Kuzawa, 2007; Mell et al., 2018; Shulman & Connolly, 2013; Young, 2003). Previous research suggests that early environmental instability and lack of parental involvement can influence life history strategies, leading individuals to form romantic relationships earlier in life (Ellis et al., 2009). In turn, early cohabitation in romantic relationships may be correlated with negative individual health and well-being. Higher-education environments, despite their evolutionary novelty, present an opportunity for researchers to better understand how family dynamics are associated with adult relationship strategies and to understand the developmental correlates of such strategies. Our study focuses on how parental involvement is associated with adult mating strategy and developmental outcomes—specifically, one important developmental transition—cohabitating with a romantic partner. Emerging adulthood is a particularly vulnerable time, and because of this, is often one accompanied by continued kin support (Hochberg & Konner, 2020; UNESCO, 2013).

Thus, the present study was designed with two goals in mind: (a) explore how environmental stressors (e.g., daily stressors) and family experiences (e.g., parental involvement, family financial support) are associated with the formation of early cohabitating relationships, and (b) determine the physical and mental health correlates of early cohabitation. Specifically, we aimed to examine how parental involvement and daily stress contribute to the timing and nature of relationship formation in emerging adulthood. Furthermore, we investigated how early cohabitation impacts mental and physical health correlates, considering both the benefits and risks outlined above. By understanding these correlates, we can better comprehend the long-term implications of early cohabitation on individual health and well-being. Low parental involvement and daily stress were expected to be associated with cohabitation, and early cohabitation was expected to negatively impact mental (depression, emotion regulation and risky behavior) and physical health (BMI).

Method

Sample and Procedure

This study was conducted in accordance with the ethics guidelines of the Institutional Review Board at (location masked) and pertinent to Federal regulations for the protections of human subjects as implemented by the United States Department of Health and Human Services (HHS); clinical trial number not applicable. The original sample consisted of 869 college students. Because only a small subsample of participants (n = 7) reported being married, and we were interested in studying unmarried college students, the married participants were removed from the sample. The final sample for this study consisted of 862 college students (Age range = 18–25; Mage = 19.52, SD = 1.33). The sample was 57.8% female; 4.4% dating and living together (n = 38), 31.7% dating and not living together (n = 273), 63.9% single (n = 550). Participants were 76.2% European American, 7.1% African American, 5.3% Hispanic American, 3.1% Asian American, 6.0% Native American, 2.3% other including self-identified biracial individuals. They had a Mdn yearly income $4,050, SD = $17,056, and percentage of total living expenses paid for by parent/family (range = 0 to 100) was M = 62.34, SD = 39.23. Most primary caregivers were biological mothers (biological mothers = 88.7%, biological father = 7.5%, adoptive/step/foster mother = 1.4%, grandparent = 1.3%, other = 1.1%). Based on presidential voting (Republican candidates selected since 1968) and political parties in the state legislature (81.5% republican), the college sample was recruited in a mostly conservative southern U.S. state (reference masked). In addition, according to research by the Pew Research Center, 47% of respondents from the state self-identified as evangelical Christian, which was ranked the fourth highest in the country (Pew Research Center, 2015). In 2023, the university student body was mostly European American (70%) with 30% ethnic minority students (5% African American, 6% Hispanic American, 2% Asian American, 5% Native American, 9% two or more races, 3% other ethnic groups) (reference masked).

The data were collected through online anonymous surveys during the spring and fall semesters of 2019. The participants were recruited through the SONA system in the psychology department at [location masked]. Participants were credited 1 research hour for completing the 30–45-minute survey. Participants provided consent online by selecting “Yes” regarding their willingness to participate in the study. Because the data were anonymous, no signed consent forms were collected. The project was approved by the [location masked] Internal Review Board. Data from this investigation are available upon request to the first author.

Materials

Predictors of Early Cohabitation

Parental Involvement

Parental involvement refers to the frequency with which the emerging adult and primary caregiver spend time together during the past year and generally reflects positive experiences within the dyad. The 10-item measure (e.g., “Do something fun together.” “Eat a meal together.”) was developed by Criss et al. (2015) who reported adequate internal consistency and predictive validity for the measure. The items were rated on a 5-point scale (1 = never to 5 = very often). The parental involvement factor was computed by averaging (α = 0.93) the 10 items with high scores reflecting high levels of parent-emerging adult involvement.

Daily Stress

Daily stress was based on the Perceived Stress Scale (PSS; Cohen et al., 1983) which demonstrated adequate internal consistency and predictive validity according to Cohen et al. (1983). The 10-item instrument (e.g., “How often have you felt nervous and “stressed”? “How often have you felt difficulties were piling up so high that you could not overcome them?”) reflects the extent to which the participant experienced daily stress and tension during the past year. The items were rated using a 5-point Likert scale (0 = never to 4 = very often). The daily stress factor was created by averaging (α =.93) the 10 items with high scores reflecting high levels of daily stress.

Correlates of Early Cohabitation

Body Mass Index (BMI)

Emerging adult BMI is defined as the body-to-height ratio ranging from low (i.e., underweight) to high (i.e., obese) scores based on current height and weight. Based on participants’ self-reported height and weight, the BMI score was computed using an on-line calculator (https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm).

Depressive Symptoms

Emerging adult depressive symptoms were assessed using the 20-item Center for Epidemiological Studies Depression Scale (CES-D; Radloff, 1977) which demonstrated adequate reliability and validity (Radloff, 1977). The items measured participants’ feelings or things the participant experienced doing over the last week or so and included items such as “I felt depressed,” “I felt lonely,” and “I had crying spells.” The items were rated on a 4-point Likert scale: 0 = rarely or none of the time (less than 1 day), 1 = some or little of the time (1–2 days), 2 = occasionally or a moderate amount of the time (3–4 days), 3 = most or all the time (5–7 days). The clinical cut-off point for the CES-D is 21 (Henry et al., 2018). Emerging adult depressive symptoms factor was created by summing (α = 0.88) the 20 items with high scores reflection high levels of depressive symptoms.

Emotion Regulation

Emotion regulation reflects the degree to which the emerging adult was able to successfully modulate negative (i.e., anger, sadness) emotions during the past year. Following published studies using adolescent (Cui et al., 2020) and emerging adult (Esparza et al., 2024) samples, sadness and anger regulation were assessed in the current study using an instrument based on Children’s Emotion Management Scale: Sadness and Anger Scales (CSMS, Zeman et al., 2001; Zeman et al., 2002). Adequate internal consistency and predictive validity for the anger and sadness subscales were reported by Zeman (Zeman et al., 2002). Sadness regulation was based on four items (e.g., “I stay calm and don’t let sad things get to me.” “I try to calmly deal with what is making me feel sad.”), and anger regulation was assessed using four items (e.g., “I can stop myself from losing my temper.” “I try to calmly deal with what is making me feel mad.”). The sadness and anger regulation items were rated using a three-point rating scale (0 = not true, 1 = somewhat true, 2 = very true). Emerging adult sadness regulation (α = 0.78) and emerging adult anger regulation (α = 0.84) were both created separately by averaging the four items with high scores reflecting high levels of emotion regulation.

Risky Sexual Behavior

Emerging adult risky sexual behavior reflects the frequency with which the emerging adult engaged in risky and promiscuous sexual behavior during the past year. This factor was adapted from the Risky, Impulsive, and Self-Destructive Behavior Questionnaire (RISQ; Sadeh & Baskin-Sommers, 2017) which demonstrated adequate internal consistency and construct validity (Sadeh & Baskin-Sommers, 2017). Using a 5-point Likert scale (1 = never, 2 = 1–2 times, 3 = 3–4 times, 4 = 5–6 times, and 5 = 7 or more times), participants reported how often during the past year that they engaged in 8 risky sexual behaviors, all considered risky even in the context of a long-term relationship (e.g., “During the past year, how many times did you have unprotected sex with someone you just met or did not know well?” “During the past year, how many times did you hook up with someone you did not know well for sex?”). In addition to rating the 8 items, the participants provided the number of total sexual partners that they have had (1) during the past year (M = 1.40, SD = 1.69) and (2) during their entire life (M = 3.38, SD = 4.55). The emerging adult risky sexual behavior was computed by standardizing (due to different scales) and averaging (α = 0.85) the 10 items with high scores reflecting high levels of risky sexual behavior.

Analytical Plan

Descriptive statistics and bivariate correlations among the study variables were computed. To address the first research question, to explore how environmental stressors and family experiences are associated with the formation of early cohabitating relationships, a multinomial logistic regression was computed in which emerging adult relationship status (dating and living together, dating and not living together, or single) was predicted by daily stress, parental involvement, EA gender, EA ethnicity, and the percent of expenses paid for by parents which were entered simultaneously in the analysis. For multinomial logistic regressions, one first ascertains whether the overall analyses are significant (via chi-square analysis). Next, one investigates whether the predictors are significantly and incrementally related to the dependent variable (i.e., emerging adult relationship status). Finally, the output from multinomial logistic regression analyses includes group-specific odds ratio estimates affording the ability to make comparisons regarding group membership. Following the recommendations of Brendgen et al. (2005) and Trentacosta et al. (2011), we focused only on the odds ratio estimates for significant predictors of emerging adult relationship status.

Then, to address the second research question, to determine the physical and mental health correlates of early cohabitation, a series of analyses of covariance (ANCOVAs) were computed in which emerging adult adjustment (BMI, depressive symptoms, emotion regulation, or risky sexual behavior) was predicted by emerging adult relationship status (dating and living together, dating and not living together, or single) controlling for emerging adult gender. Finally, in a set of exploratory analyses, a series of independent t-tests were calculated analyzing whether there were significant differences between dating and living together emerging adults and dating and not living together emerging adults with respect to demographic characteristics (i.e., partner age, length of knowing romantic partner, length of dating romantic partner, emerging adult average hours worked per week, and total expenses paid for by emerging adult parents).

Results

Bivariate Correlations and Descriptive Statistics

Bivariate correlations and descriptive statistics are located in Table 1. The descriptive statistics indicated that 27.3% of the sample scored above the clinical cut-off score of 21 for depressive symptoms (Henry et al., 2018). The pattern of bivariate correlations between family characteristics and emerging adult outcomes were consistent with expectations. Specifically, high levels of daily stress were significantly related to high levels of body mass index, depressive symptoms, and risky sexual behavior and low levels of sadness regulation and anger regulation. Also, parental involvement was negatively and significantly related to body mass index, depressive symptoms, and risky sexual behavior. Findings also indicated that daily stress, parental involvement, and depressive symptoms were significantly higher among women whereas sadness regulation was significantly higher among men. Correlations also indicated that high levels of percent of expenses paid for by parents was significantly related to high levels of parental involvement and low levels of EA body mass index and depressive symptoms.

Table 1 Bivariate correlations and descriptive statistics
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Family Characteristics of Emerging Adult Relationship Status

For the first research goal, we investigated whether daily stress and parental involvement significantly differentiated membership in the emerging adult relationship status groups when examined simultaneously. The multinomial logistic regression was significant, χ2(10) = 48.84, p <.001, Negelkerke R2 = 0.07. As indicated in Table 2, daily stress, parental involvement, EA ethnicity, and percentage of expenses paid by parents were significantly and incrementally related to emerging adult relationship status group membership. Emerging adult gender was not significant in this analysis. The group specific odds ratio estimates showed that high levels of daily stress and low levels of parental involvement and percent of expenses paid by parents significantly increased the odds of being in the dating and living together group compared to dating and not living together and single relationship groups. In addition, being an ethnic minority significantly increased the odds of being in the dating and not living together groups compared to the single group. None of the other odds ratio estimates were significant.

Table 2 Multinomial logistical regressions examining predictors of emerging adult relationship status group
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Emerging Adult Adjustment Correlates of Relationship Status

The second research goal was to examine emerging adjustment correlates of relationship status. A series of ANCOVAs were computed separately for each outcome variable to investigate (adjusted) mean differences across emerging adult relationship status with EA gender, EA ethnicity, and percentage of expenses paid for by parents entered as covariates. Findings from the first ANCOVA indicated that emerging adult relationship status was significantly related to emerging adult body mass index scores (see Table 3). The Bonferroni pos-hoc analyses indicated that members of the dating and living together group had significantly higher levels of body mass index scores in comparison to the dating and not living together and single relationship groups. Findings also indicated that emerging adult relationship status was marginally significantly related to emerging adult depressive symptoms. Although members of the dating and living group had the highest levels of depressive symptoms, none of the Bonferroni post-hoc analyses were significant. Turning to the next ANCOVA, findings indicated that emerging adult relationship status was significantly related to both sadness regulation and anger emotion regulation. Bonferroni post-hoc analyses indicated that members of the dating and living together group reported marginally significantly lower levels of emotion regulation compared to members of the single group. The results also demonstrated that EA relationship status was significantly related to emerging adult risky sexual behavior. Bonferroni post-hoc analyses indicated that members of the dating and living together group reported significantly higher levels of risky sexual behavior compared to members of the single group.

Table 3 Analyses of covariance examining the link between relationship status and EA adjustment controlling for gender, ethnicity, and expenses paid by parents
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Comparison of Two Dating Subgroups

In exploratory analyses, we analyzed whether there were significant differences between the two dating subgroups: dating and living together and dating and not living together. As indicated in Table 4, compared to the dating and not living together group, the dating and living together group reported significantly higher levels of partner age, age difference between partner and emerging adult (marginally significant), length of knowing romantic partner, length of dating romantic partner, and hours the EA worked per week and significantly lower levels of percentage of total expenses paid by parents.

Table 4 Independent t-tests examining differences between dating/living together and dating/not living together emerging adults
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Discussion

The purpose of this study was to better understand the family relationships associated with early cohabitation, and the implications of cohabitation early in emerging adulthood on individual health and well-being. Specifically, we aimed to examine how parental involvement contributed to the timing and nature of relationship formation in emerging adulthood, and, in turn, how early cohabitation was associated with physical and mental health correlates among college students living in a Southern U.S. state. Compared to their peers who were either single or dating but not cohabitating, emerging adults cohabitating with their partner had higher BMI, more depressive symptoms, risky sexual behavior, and poorer emotion regulation. Those living with their partners were also distinct from their peers in that they had higher daily stress and lower parental involvement. This is consistent with an “alternate” fast life history strategy in which emerging adults are compensating for lack of kin support in this vulnerable transitional stage.

Parental Involvement

Emerging adults who experienced more daily stress and who had less social and financial investment from their parents were more likely to be living with their romantic partner compared with emerging adults with less adversity and more parental investment. These findings are consistent with findings related to sexual debut (Dunkel & Lukaszewski, 2015; James et al., 2012). Life history theory predicts that early life experiences and level of parental support serve to attune development toward most adaptive pathways considering the constraints of predictability and parental/kin support (Shulman & Connolly, 2013; Mell et al., 2018) and this should not preclude the psychosocial development of emerging adulthood (Ellis et al., 2009). These individuals also were working more hours outside of school, presumably compensating for lack of parental support, and had higher daily stress levels, consistent with previous findings (Thompson & Prottaset, 2006). While relationships can buffer the impact of daily stressors (Uchino, 2006), the quality of the relationship is integral to the relationship between social support, stress, and health outcomes (Whitton & Kuryluk, 2012). Though we did not directly measure romantic partner relationship quality, our results suggest that those cohabitating with their partners may have accelerated the relationship to gain social support (Ellis et al., 2009).

Physical and Mental Health Correlates of Early Cohabitation

It is important to point out that the trade-offs evident in this study were consistent adaptively patterned psychosocial development when family support is low, despite the associated costs. Health disparities, particularly diseases associated with inflammation, like obesity, are often evident in individuals from environments with low social support, as these environments constitute a type of social adversity that propels disease processes (Cohen, 2004; Slavich, 2022; Wilkinson, 1996). This may reflect a compromise between attaining necessary support to successfully navigate the developmental phase of emerging adulthood and lacking access to stable relationship partners. Those cohabitating at this stage had health patterns with higher BMI, more evidence of depression, lower emotion regulation, and reported more risky sexual behavior, patterns consistent with an accelerated life history strategy (Del Giudice et al., 2011; Dinh et al., 2022).

Emerging Adulthood as a Life History Stage

Emerging adulthood has been posited as a distinct life history stage, and one that may have been integral for the relatively high reproductive success that humans accomplish in comparison to the other great apes (Hochberg & Konner, 2020). In fact, even in traditionally living small-scale societies, most individuals up to the age 24 have not fully assumed adult roles (Hochberg, 2012; Sawyer et al., 2012). The United Nations has identified this time in development (15–24) as a period of vulnerability and priority for interventions worldwide (UNESCO, 2013), suggesting that our culturally-derived understanding of adulthood beginning at 18 is woefully inaccurate. This is likely because despite the extensive neural reorganization that occurs during this developmental stage, individuals have the physical appearance of adults (Hill et al., 2010) but are not yet fully mature. In other words, the final stages of development prior to adulthood occur in the brain.

Ideally, emerging adulthood is a time of learning about intimacy, mutual support and socialization with intense focus on friendships, but continued family support (albeit at a distance). Our findings suggests that lack of support from family make this stage difficult to navigate. Individuals are developing awareness of political and cultural influences and attaining social and economic skills needed for successful execution of adult stage tasks (Haan et al., 1968). Traditionally, extended families were crucial in giving emerging adults the protection they needed to complete development, making it a unique human life history trait (Kaplan & Robson, 2002). Although women often reach first reproduction during this period in traditional foraging societies, they are heavily provisioned by mature adults, often post-reproductive adults (e.g., grandmothers) and their partner, who is often several years older (Hawkes, 2003; Hawkes et al., 1997; Marlowe, 2003; Howell, 2010). In other words, emerging adulthood appears to represent a distinct period in human development that is vulnerable and requires substantial social support to navigate. In developed societies, there is a mismatch between earlier sexual maturity and the slow maturation of the of the prefrontal cortex (Gluckman & Hanson, 2006), potentially representing a decoupling of pubertal and brain maturation. This mismatch may result in emerging adults appearing more socially and occupationally competent than they are. However, we know little about this stage outside of college populations. Therefore, future studies should incorporate emerging adults in differing contexts like trade schools, community colleges, in addition to including those who did not graduate from high school and who are in the workforce to disentangle these effects and determine if the same detrimental health outcomes exist among those cohabitating in these contexts.

Limitations and Future Directions

Although the focus of this study was on factors influencing life history and relationship strategies in emerging adulthood, it is limited to a sample of college students living in a predominantly conservative and Evangelical Christian state, in which cohabitating with a romantic partner may be more atypical than in other regions (Gault-Sherman & Draper, 2012). Examining this transition in a broader sample of emerging adults, specifically those entering the work force full time and living in other states or countries would enable us to have a more accurate understanding of the factors influencing health and psychosocial outcomes during this unique developmental stage. Our sample may have been limited to those individuals who are capable of navigating higher education environments despite the adversity and associated costs they faced, and therefore not be representative of the overall population. In addition, although this study utilized a large sample, its cross-sectional design would have limited the ability to determine directionality of the links. Future research would benefit from longitudinal studies. Finally, this investigation is not exhaustive in terms of other factors relevant to life history strategies, as there are economic and regional factors that play an important role in determining the strength of the relationship between early environments and health outcomes.

Conclusions

We sought to better understand the links between family relationships with early cohabitation, and, by extension, the implications of early cohabitation. Our findings showed that daily stress and low parental involvement predicted a pattern of early cohabitation and negative physical and mental health impacts. These findings extend the well-developed literature on determinants of life history strategies to the uniquely human and often neglected stage of emerging adulthood. Our pattern of results suggests that some individuals attempt to compensate for lack of parental involvement and support while they attempt to gain socio-cognitive skills (e.g., higher education) with romantic partner support and that this strategy has some trade-offs. These findings have implications for health professionals, particularly those who service college-aged emerging adults.