Well-Being and Romantic Relationships: A Systematic Review in Adolescence and Emerging Adulthood

Adolescence and emerging adulthood are both stages in which romantic relationships play a key role in development and can be a source of both well-being and negative outcomes. However, the limited number of studies prior to adulthood, along with the multiplicity of variables involved in the romantic context and the considerable ambiguity surrounding the construct of well-being, make it difficult to reach conclusions about the relationship between the two phenomena. This systematic review synthesizes the results produced into this topic over the last three decades. A total of 112 studies were included, following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) guidelines. On the one hand, these works revealed the terminological heterogeneity in research on well-being and the way the absence of symptoms of illness are commonly used to measure it, while on the other hand, they also showed that romantic relationships can be an important source of well-being for both adolescents and emerging adults. The findings underline the importance of providing a better definition of well-being, as well as to attribute greater value to the significance of romantic relationships. Devoting greater empirical, educational, and community efforts to romantic development in the stages leading up to adulthood are considered necessary actions in promoting the well-being of young people.


Introduction
Since World War II, most conceptualizations of health have been focused on the absence of illness and disability [1]. Psychology was concentrated on repairing damage within a disease model of human functioning [2], paying almost exclusive attention to pathology and neglecting the study of the positive features that make life worth living [2]. It is currently known that the absence of pathology does not necessarily correlate with positive dimensions of health and well-being [3,4], and psychologists have begun to admit well-being as a relevant aim of study, as well as the factors that contribute to its encouragement [5]. Positive psychology was recently established as a new perspective specifically addressing the study of well-being, quality of life, strengths, and resources [2,6]. Within this framework, diverse approaches have emerged. In a general sense, well-being can be understood as optimal psychological functioning and experience [7]. More specifically, some theorists have defined it as a state characterized by a high degree of satisfaction with life and the experience of high levels of positive affect [8], while others have focused on the notion of a process of fulfilling human potentials, capacities, and virtues [7]. Despite this systematization of the theory, the diversity of terminology found in the different studies has led to a certain degree of controversy. Although, admittedly, this situation has contributed to a productive scientific debate, it has also led to considerable ambiguity and theoretical and methodological confusion. On the other hand, these approaches represent mainly personal evaluations of what well-being means, and they deal only fleetingly with the social dimension of the individuals involved. In this sense, it has been previously established that the desire for interpersonal attachment (the need to belong) is a fundamental human motivation [9], especially when it refers to romantic relationships. So important is relatedness that some theorists have defined it as a basic human need, essential for well-being [9][10][11][12]. For example, in their 2002 study, Diener and Seligman examined extremely happy people to determine necessary conditions for entering this group [13]. They found that good and strong personal relationships were ubiquitous in these people. Nevertheless, the topic of relationships is complex and close relationships are multifaceted, justifying with this a study of specificity, in terms of the aspects of relationships that can promote well-being [7].

Romantic Relationships and Well-Being in Adolescence and Emerging Adulthood
From an evolutionary point of view, adolescence and emerging adulthood (the periods which span the second and third decades of life [14,15]) have been described as being vitally important in terms of the development of romantic relationships [16][17][18]. Defined as "mutually acknowledged ongoing voluntary interactions" [18,19], these relationships, unlike others such as friendships, are characterized by a particular intensity, specific expressions of affection, and initiation in erotic sexual encounters [19]. Previous studies have shown that these experiences are frequent during adolescence and tend to consolidate over time [20,21], representing an important context for learning and training for future intimate relationships [14]. By middle adolescence, most boys and girls have been involved in at least one romantic relationship [21], providing them with a scenario characterized by greater intimacy, support, and importance as their age advances [22,23]. As adolescents approach emerging adulthood, the time they devote to their romantic partners increases [24,25], and they use these relationships to look for company, emotional security, intimacy, and the feeling of love they provide, until they reach a stage when they are ready to take decisions over questions of long-term commitment, such as cohabitation and marriage [26,27]. According to the developmental task theory, during adolescence, romantic involvement is an emerging developmental task, which will eventually become a salient developmental task in adulthood [28].
Romantic relationships and experiences are important sources of emotional bonding and contribute to the development of a positive self-concept and greater social integration [29,30]. The successful establishment and maintenance of romantic relationships can have important repercussions in later stages of life [15], and has been described to contribute to people's mental and physical health and, therefore, to their well-being [31]. From this perspective, romantic relationships, when sustained over time, constitute a transformation of the attachment bond. The quality of the relationship, the history of the shared experiences, the sense of attachment, and the beliefs which arise from the whole experience have all been recognized as modulating the well-being of the partners [32][33][34][35][36][37][38][39][40]. Despite the fact that the wide range of aspects mentioned in the research makes it difficult to establish how direct an effect these relationships have on well-being, there is a broad consensus in the literature that love is one of the strengths most closely linked to personal happiness [41,42], and is associated with higher rates of self-esteem, safety, satisfaction with life, positive affect, and achievement of personal and relational goals [43][44][45][46]. However, romantic relationships have also been associated with negative outcomes, especially during adolescence. Thus, studies have suggested that romantic involvement may be related to the presence of different forms of violence [47][48][49][50], experiencing internalizing symptoms such as depression or anxiety (e.g., [37,51,52]), poorer psychosocial functioning [53], or delinquency [54].

The Present Study
Following these considerations, the empirical evidence suggests the important role that romantic relationships can play in people's well-being, however, the number of studies focusing on stages prior to adulthood remain relatively limited, consequently not providing clarifying results. Moreover, the wide range of intervening variables in the romantic context and the relative ambiguity of the concept of well-being make it difficult to draw conclusions. Therefore, a work of synthesis is required to gather together the accumulated empirical knowledge and facilitate an understanding of the findings made so far in relation to the association between well-being and romantic relationships in adolescence and emerging adulthood. To do this, the general aim of this study was to carry out an exhaustive review of the existing literature in order to delve deeper into this topic. In particular, a specific aim was established: To identify the variables of romantic relationships that studies have associated with the well-being of young people.

Literature Search and Quality Assurance
A structured search was carried out between July and September 2017 in the following databases of high-quality standards, which include peer-reviewed studies: Scopus, Web of Science, PsycINFO and Scielo. The Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) Declaration was applied [55], following its protocol for the planning, preparation, and publication of systematic reviews and meta-analyses [56]. The search terms used included keywords in Spanish and English which were considered to be indicators of well-being (bienestar*, well-being*, wellbeing*, "wellbeing", felicidad*, happiness*, "fortalezas psicológicas", "psychological strengths", florecimiento*, flourishing*, "desarrollo positivo", "positive development") and keywords linked to romantic relationships (dating*, "relaciones sentimentales", "sentimental relationships", "relaciones románticas", "romantic relationships", cortejo*, courtship*, "relaciones íntimas", "intimate relationships"). In order to achieve a comprehensive overview of the state of research in this field, the search did not include any specific terms (e.g., psychological well-being, subjective well-being, hedonia, eudaimonia, hooking up, friends with benefits, etc.).

Inclusion/Exclusion Criteria
The inclusion criteria were established following the PICOS (acronym for Participants, Interventions, Comparisons, Outcomes and Study design) format [57]: a.
Type of participants: Adolescents and emerging adults of both sexes, ranging in age from 13 to 29 years old, or those whose average age is included in that range, with no known mental disorders, and those of any origin or nationality. b.
Type of studies: Empirical studies written in English or Spanish and published in peer-reviewed journals. c.
Type of outcome measurements: In a first stage, studies were included which made explicit reference to the search descriptors in the title, summary, and/or keywords. In a second stage, studies were included with specific analyses of the link between romantic relationships and any of the previous indicators. d.
Type of designs: Quantitative and qualitative.
Additional exclusion criteria included theoretical studies, doctoral theses, systematic reviews, meta-analyses, book chapters, reports from conferences or symposia, letters to the editor, minutes of meetings or informative notes, and studies in which the authors did not provide information about the participants' age.

Data Coding and Extraction
Three matrices of documentary records were created specifically for this work. In the first, quantitative data on the search results were collected for each database consulted and each of the descriptors used. In the second, information was gathered from each selected or unselected study (e.g., title, author/s, year of publication, sample size, age of participants, study objectives, methodology, or reason for exclusion, where appropriate). The third recorded the well-being measures and the specific variables of the romantic context analyzed by the studies. The selection of studies was performed in different stages [58] (Figure 1). The identification stage was limited to articles published in English and Spanish between 1990 and 2017 (inclusive). This first phase yielded a total of 3229 studies. In the screening stage, the duplicates were discarded, which left a total of 2866 studies. Next, two reviewers selected the studies whose title, summary, or keywords contained any of the search descriptors used, which produced a total of 461 eligible studies and a total of 2405 rejected studies. In the eligibility stage, all the reviewers independently assessed the full text of the potential studies to be included, initially reaching a level of agreement of over 90% and resolving any discrepancies through a process of discussion and consensus. In the included stage, the three reviewers jointly agreed on the full sample of studies, resulting in a total of 112 studies. The software packages Mendeley version 1.17.12 (Elsevier Inc., New York, NY, USA) and SPSS version 22 (IBM Corp., Armonk, NY, USA) were used to carry out the process of coding and obtaining the results. stage, the duplicates were discarded, which left a total of 2866 studies. Next, two reviewers selected the studies whose title, summary, or keywords contained any of the search descriptors used, which produced a total of 461 eligible studies and a total of 2405 rejected studies. In the eligibility stage, all the reviewers independently assessed the full text of the potential studies to be included, initially reaching a level of agreement of over 90% and resolving any discrepancies through a process of discussion and consensus.
In the included stage, the three reviewers jointly agreed on the full sample of studies, resulting in a total of 112 studies. The software packages Mendeley version 1.17.12 (Elsevier Inc., New York, NY, USA) and SPSS version 22 (IBM Corp., Armonk, NY, USA) were used to carry out the process of coding and obtaining the results.

Characteristics of the Included Studies
This work has reviewed nearly three decades of research (1990-2017) on well-being and romantic relationships during adolescence and emerging adulthood. Of the 112 studies included (see Table 1), 9% were published in the 1990s, 27% in the first decade of this century, and 64% were published since 2010. The total number of participants was 278,871, with the amount of participants ranging from 30 in some studies [59,60] to 81,247 participants in another [47]. The general age range was from 12 to 70 years, with the average age never surpassing 29 years in any of the studies. Overall, 83% of the studies (n = 93) were directed at emerging adulthood, while 17% (n = 19) focused on adolescence. Regarding the well-being measures observed, the studies analyzed used as many as 142 different variables, of which the most commonly employed were life satisfaction (35.3%), depression (25%), affect (positive and negative, 22.8%), self-esteem (17.6%), relationship satisfaction (15.4%), anxiety (11%), happiness (8.1%) and stress (5.9%).

Characteristics of the Included Studies
This work has reviewed nearly three decades of research (1990-2017) on well-being and romantic relationships during adolescence and emerging adulthood. Of the 112 studies included (see Table 1), 9% were published in the 1990s, 27% in the first decade of this century, and 64% were published since 2010. The total number of participants was 278,871, with the amount of participants ranging from 30 in some studies [59,60] to 81,247 participants in another [47]. The general age range was from 12 to 70 years, with the average age never surpassing 29 years in any of the studies. Overall, 83% of the studies (n = 93) were directed at emerging adulthood, while 17% (n = 19) focused on adolescence. Regarding the well-being measures observed, the studies analyzed used as many as 142 different variables, of which the most commonly employed were life satisfaction (35.3%), depression (25%), affect (positive and negative, 22.8%), self-esteem (17.6%), relationship satisfaction (15.4%), anxiety (11%), happiness (8.1%) and stress (5.9%). As efficacy expectations shared between partners increased, the degree of their life satisfaction also increased. Minority stress components were negatively related to well-being, however, the impact of "expected rejection" on well-being was buffered for those involved in a romantic relationship.
[ Tendency to compromise during problem-solving was associated with less depressive mood among people who subsequently were more satisfied with their relationship.
Implicit attitudes towards partners correlated significantly with explicit attitudes, secure attachment, and well-being.
[  Autonomy, environmental mastery, personal growth, positive relationships, purpose in life, self-acceptance (Ryff's model of psychological well-being); life satisfaction and affect-balance.
Authenticity was related to engaging in healthy relationship behaviors, which in turn predicted positive relationship outcomes and greater well-being.
Self-determined sexual motivation, sexual need satisfaction, well-being, and relational quality were positively intercorrelated.
Men's and women's self-determined sexual motivation predicted their own well-being, and men's self-determined sexual motivation also predicted women's well-being.
Adolescents in violent relationships are more likely to experience negative well-being outcomes. Increasing levels of dating violence were related to higher levels of post-traumatic stress and dissociation in girls. Victimization was related to higher levels of anxiety, depression, and post-traumatic stress in boys.
[ Negative appraisals of breakups were associated with lower well-being. Positive appraisals were associated with greater anxiety symptoms, self-esteem, and a sense of personal competency.
Being in a dating relationship was associated with less alienation, more positive views of the self, and higher general expectations for success. Among sexually active youth, daters had lower levels of depression than non-daters.
[82] 12,841 18-32, NR (NR) Earnings, high relative income, and stability of employment histories. Well-being had a weaker association with cohabitation than with marriage.
Among girls, dating violence victimization was associated with poor health-related quality of life and suicidal ideation or attempts. Among boys, dating violence perpetration was associated with a poor health-related quality of life and suicide attempts, and lower scores of life satisfaction. Limiting people's attention to attractive alternatives reduced relationship satisfaction and commitment and increased positive attitudes toward infidelity.
Sexual-minority youths had comparable self-esteem, mastery, and perceived stress as did heterosexuals, but greater negative affect.
[13] 222 College students Life satisfaction and affect balance. Well-being was positively associated with good-quality relationships.
[ A high and mutual commitment to the relationship was positively related to greater adjustment. Romantic relationships characterized by inequality in the contribution of emotional resources and in decision-making, were associated with greater psychological symptomatology. Communal coping was unrelated to psychological distress. Partner overinvolvement in diabetes management had a mixed relation to outcomes, whereas partner under involvement was uniformly related to poor outcomes. Approach sex motives were positively associated with well-being, while avoidance sex motives were negatively associated.  Communication had a beneficial effect on both the individual and the dyadic level in the context of existence of sexual problems.
Interracial daters had greater odds of risk for depression than their non-dating and same-race dating peers. Experiencing a romantic breakup explained the elevated risk of depression for daters in general, and same-race daters specifically, but not interracial daters.  Happiness with the marriage, satisfaction with the marriage, happiness with the level of equity in the marriage, perceived stability of the marriage, perceived certainty that they would still be married in 5 years, and frequency of thoughts of leaving the spouse.
Reporting abundant and positive experiences and giving positive meaning to them were associated with improved levels of well-being over time.   Autonomy, environmental mastery, personal growth, purpose in life, positive relationships, and self-acceptance (Ryff's model of psychological well-being).
Positive relationship quality was found to be a mediator between forgiveness (seeking and self) and well-being. Low attachment anxiety in romantic relationships predicted happiness; low attachment anxiety and high self-efficacy predicted low psychological distress; less fear of negative evaluation from the partner and high self-efficacy positively predicted self-esteem.

Variables of Romantic Relationships Related to Well-Being in Adolescence and Emerging Adulthood
Achieving the specific aim of this study involved reviewing the variables of romantic relationships which have been associated with well-being during adolescence and emerging adulthood. These variables were sorted into two categories: First, the label "relational variables", where studies analyzing characteristics of romantic relationships and the processes that take place within them were grouped. Secondly, the label "personal variables", which gathered the studies that examined individual variables involved in establishing, forming, and/or developing romantic relationships (see Table 2).
A total of 87 studies analyzed the association between romantic relationships and well-being based on relational variables. Relationship status, relationship quality, and relationship history and experiences were the variables most commonly focused on in the studies. In general, particularly during emerging adulthood, participants involved in a romantic relationship showed higher levels of well-being than those who were single. More specifically, it was suggested that staying single, either voluntarily or involuntarily, and remaining so in order to avoid the negative consequences of relationships (avoidance goals) was not associated with well-being, with the best predictor being satisfaction with that status. Particular aspects of relationship status, such as the stability of the relationship or the experience of splitting up, have been widely studied. Studies that equated commitment to romantic status suggested that a higher level of commitment or stability in the relationship (marriage vs. cohabitants, non-marital relationships, casual relationships, etc.) leads to a greater well-being. In this regard, a specific case analyzed was hook-up experiences. These expressions of sexuality, outside the context of a committed relationship, were only negatively associated with well-being in one study. Similarly, the experiences of separation or divorce have been identified with increased well-being if these events were evaluated positively, if the quality of the relationship was poor, or if a new relationship started shortly after the separation.
Along similar lines, the studies also evaluated the role of well-being in relationship quality, with relationship satisfaction, commitment and intimacy being the most common indicators. Throughout the periods of adolescence and emerging adulthood, high levels of quality in the relationship were positively associated with well-being, while, similarly, low levels of quality were linked to negative effects. In cases of transgression, the quality of the relationship was also identified as a mediator between forgiveness and the well-being of the transgressor. Close to the findings regarding relationship quality are those associated with relationship history and experiences. The studies in this line showed that reporting and remembering a large number of positive experiences, such as shared laughter, being at a formal or positive relational turning point, or expressing gratitude towards the partner, were all positively associated with well-being, while negative experiences, such as arguments, transgressions, power imbalance, or violence, were associated with a decrease in well-being levels.
When considered independently and not as indicators of the relationship quality, rates of commitment and intimacy between partners have also been identified as variables which can influence well-being: High levels of commitment to the relationship and intimacy between romantic partners were positively associated, where low levels of commitment showed an inverse relationship. Likewise, romantic attachment can also have important implications. The studies indicate that a secure romantic attachment would be most beneficial, while avoidant and anxious attachment have been suggested as reliable predictors of low levels of well-being.
Communication and conflict resolution between partners have both been identified as variables with a significant effect on well-being. On one hand, the disclosure of sexual problems and receiving positive body feedback from the partner were both positively associated with well-being, while on the other hand, showing high levels of positive affect in conflict situations was found to be a good predictor of relationship stability and satisfaction. Likewise, self-compassion and dyadic empathy (empathy specifically expressed towards the romantic partner) were variables found to have a positive effect, where more self-compassionate individuals were more likely to resolve interpersonal conflicts by balancing their needs to their partner's needs, feeling more authentic and less emotionally turmoiled.
Similarly, high levels of empathy in couples in the transition to parenthood led to improved levels of well-being in the partners.
Variables concerning need fulfillment and achieving relational and personal goals have also been identified as related to well-being. A partner's support to personal needs of autonomy, competence, and relatedness (Self-Determination Theory [8]), or the maintenance of relational behaviors driven by self-determined motives, were positively associated with well-being. Similar results were found in relation to the effects of the achievement of the ideal self and the congruence of the goals between partners. According to the studies, romantic partners can significantly influence what we become, having important implications for well-being, as well as the pursuit and involvement in activities aimed to achieve shared goals.
In the studies conducted during adolescence, violence occurring within the relationship (dating violence) in either form, both as a victim and as a perpetrator, has emerged as a highly significant negative variable for well-being, being associated to symptoms of anxiety, depression, stress, and low levels of self-esteem and life satisfaction, among other symptoms. Other relational variables associated with well-being during adolescence were the maintenance of same-sex relationships and interracial relationships, as well as sexuality. The negative impact caused by expected rejection due to sexual orientation was buffered by involvement in same-sex relationships, as well as improved self-esteem and decreased levels of internalized homophobia. Conversely, interracial daters were found to be more likely to suffer from depression and anxiety, as well as to perceive less support from parents and family, compared to same-race daters and non-daters. In relation to sexuality, results showed that the influence of sexual activity in depression was differentially associated with romantic status, where sexual relations associated with greater depressive symptoms corresponded to those that occurred outside the context of a romantic relationship. On the other hand, longitudinal data associated high sexual health with higher levels of well-being in adolescent girls, using indicators such as physical, mental/emotional, and social health.
To a lesser extent, the studies reviewed addressed aspects related to relationship dynamics and their association with well-being. Research into emotional interdependence (i.e., partners' emotions being linked to each other across time), shared relationship efficacy (i.e., partners' shared expectations about the joint ability to maintain satisfactorily the relationship), partner-specific perfectionism concerns, or the effect of relationships at the neurological level has rarely been contrasted with other studies. Despite this, the first two aspects were established as characteristics of healthy relationships with a positive influence on well-being, however, concerns about perfectionistic demands of the partner (perceived partner's expectations about one's own mistakes, self-criticism, and socially prescribed perfection) generated and evoked socially negative behaviors, which in turn had a deleterious effect on negative affect and life satisfaction.
Regarding the personal variables, a total of 25 works studied their relationship with well-being. Here, the variable which received the most attention was the belief system. It has been shown that, during adolescence, the imbalance between romantic expectations and reality (romantic relationship inauthenticity) is associated with a greater risk of depression and suicidal behavior, while the Sense of Coherence (SOC), a dispositional orientation or a coping resource which reflects a person's capacity to respond to stressful situations and life events, is linked with greater life satisfaction. In emerging adulthood, relationship expectations and beliefs were also suggested as factors influencing well-being. The congruence between previous expectations and reality, or between the ideal and the real romantic relationship, has been identified as a good indicator of well-being. There is no general consensus over the results for other kinds of beliefs, such as positive illusions (idealizing the partner), marriage myths, or benevolent sexism, although a number of studies have addressed them. The tendency is that the first two seem to be beneficial for well-being, while the latter showed a negative association.
Regarding cognitive, emotional, and behavioral motivation, self-forgiveness or approach and avoidance motives were revealed as indicators of well-being. According to the analyzed studies, forgiving the partner or forgiving oneself, regarding harmful relationships events, was positively related to well-being. Moreover, engaging sexually with the partner increased well-being, but only when these motives were based on approximation towards positive consequences (e.g., happiness of the partner or promoting the intimacy of the relationship) and not on the avoidance of negative consequences. Similar results were found in relation to sacrifice. Self-sacrificing aimed at achieving beneficial goals, that is, pro-social behavior which gives priority to benefits to the relationship over personal benefit, has also been positively related to well-being. Conversely, emotional suppression, limiting one's partner's attention towards attractive alternatives, or the pursuit of traditionally masculine roles (e.g., success, competition, or power) negatively affected the partner. Finally, the level of romantic competence and other skills that promote the establishment and successful maintenance of relationships, such as perceived self-efficacy, or the ability to control relational anxiety, have been strongly linked to positive results, as well as a greater ability to make better decisions and feel more confident and satisfied with the relationship.

Discussion
The main aim of this study has been to carry out a systematic review of the scientific literature on the association between romantic relationships and well-being during adolescence and emerging adulthood, focusing on identifying the specific variables associated with well-being in the romantic context.
In the first place, it is important to stress that well-being has been historically been measured in many different ways. The great number of variables observed have produced a potential problem of construct validity. It seems clear that the multiple conceptual and operational definitions used in the empirical studies on well-being hinder rather than help when it comes to defining this construct [151,152]. It is therefore important to continue trying to bring clarity to a field which is still in evolution, with previous works and new approaches still trying to be integrated [6]. Although this has its positive side, it also highlights a greater need for improving the theoretical approaches, making them more global in terms of personality and also more precise in terms of the relationship between personality traits and relational styles in romantic processes. Another aspect which may contribute to the lack of clarity in the concept of well-being is the continued use of symptoms of mental illness as an indicator. While it is true that not all of the studies reviewed used this clinical approach, but rather adopted models from positive psychology (e.g., [22,33,44,85,97,98]), there is still a prevalent tendency to conceptualize well-being in terms of the absence of disease or clinical symptoms, rather than providing a positive approximation to the concept. This is quite surprising, especially considering that it has previously been established that health and mental illness work in a relatively independent manner [153], and that the factors which make either reduce do not necessarily cause the other to increase [154]. The concept of mental health proposed by positive psychology is therefore of particular relevance here, although the definition used (the existence of a high level of well-being and the absence of mental illness) [153,155] suggests the need to develop a methodologically diverse theory which would include the full spectrum of well-being [151] and to adopt a theoretical approach according to the concepts measured, which, as of yet, none is present in the reviewed works.
In the second place, it is clear that the scientific literature stresses the importance of romantic relationships during adolescence and emerging adulthood [18,156,157], however, the small number of studies which have focused specifically on these stages show that there is a need to provide a specific psycho-evolutionary focus. Based on the works reviewed, it can be stated that romantic relationships are significantly associated with well-being in adolescents, although a number of different personal and relational variables can be understood as risk factors. A low SOC, a lack of authenticity, or the presence of violence in relationships [37,48,49,59,78,83,108,122,142], are harmful to adolescents, all of which can be explained from different perspectives. On the one hand, according to the normative trajectory model [158], early romantic experiences can compromise the well-being of adolescents when dealing with non-normative development events. On the other hand, the stress and coping model [159] postulates that romantic relationships are intrinsically challenging, requiring skills and resources that adolescents may not have. Following studies like those of [160] and [161], it is also plausible to pose the counter-argument that high levels of well-being could act as a protective factor, promoting healthy behaviors. Research with adult populations has already established this association and suggests that people with high levels of life satisfaction are more involved in intimate activities and relationships and have better relationships [13,85,162]. The association between well-being and romantic experiences during adolescence seems, therefore, to operate under a bidirectional pattern of influence, revealing with this the existence of a more complex relationship between both processes. Besides this, it is also especially important to remember that the romantic development of adolescents does not take place in a social vacuum, so it is vitally important for the well-being of adolescents to have social contexts which provide support and emotional understanding as they face the demands and challenges that this new evolutionary task lays on them [163].
Just like in adolescence, involvement in romantic relationships can be a significant source of well-being in emerging adulthood. The research reviewed suggests that young adults who have romantic relationships are happier, feel more satisfied with their lives, have fewer problems with mental and physical illness, show greater positive affect, and have better levels of self-esteem than single people. However, as noted above, the phenomenon of romantic relationships is complex and multifaceted and is associated with both relational and personal factors, and not only with their presence or absence. The relationship quality, the satisfaction of the needs of autonomy, competence and relatedness and a secure attachment with the partner have been indicated as strong indicators of well-being [7,164]. In addition, variables such as high levels of commitment, intimacy, communication, providing support to achieve personal and relational goals, good conflict management, approach motives (in contrast to avoidance), authenticity, or having strategies for coping with stressful situations, are also associated with good results, as confirmed by other studies [165,166]. Finally, personal skills and having the competence to maintain healthy and satisfying relationships are important factors which, according to some studies, can reduce symptoms of depression and anxiety, increase satisfaction with the relationship, the development of a secure attachment, and foster better decision-making. For this reason, romantic relationships based on principles of mental and emotional health and romantic competence [23,167] are considered to be among the prime sources of well-being during emerging adulthood.

Conclusions
Based on these results, one of the main conclusions from this study is the invaluable role which romantic relationships play in well-being during adolescence and emerging adulthood. As a result, this work supports their consideration as developmental assets [14]. However, the numerous benefits which are associated with them call for certain parameters to be agreed on. A relationship which is beneficial for well-being would, in general terms, have high-quality levels, through which the partners can develop their potential, achieve personal and shared goals, and maintain a secure attachment. To achieve this, people must achieve certain cognitive, emotional, and behavioral skills. It is proposed that these principles be integrated into a more parsimonious analysis, which could aid our understanding of positive romantic relationships. From this viewpoint, this study proposes romantic well-being as a new term of analysis and suggests that in future research it can be understood and evaluated as a specific category. One of the main strengths of this work, therefore, is the initial approach of a new theoretical model, termed the multidimensional model of romantic well-being, whose dimensions correspond to the particular factors which, according to the research, play an especially important role in achieving positive results, namely relationship quality, need fulfillment, the achievement of personal and relational goals, romantic attachment, and the development of individual skills.
Regarding the empirical approach to well-being, the main conclusion here is that it is necessary to understand the concept of well-being in of itself, without continually referring to a disease or symptom. This distorts the construct and prevents from relating it to dimensions which are also complex and rather diverse, such as those involved in the psycho-evolutionary task of adolescents maintaining a romantic relationship. Therefore, further research is required to establish a common, shared, and reliable theoretical and methodological framework for well-being, also allowing the ability to address the scientific study of romantic relationships in stages prior to adulthood, especially during adolescence. It is essential to adopt educational, clinical, and community models which focus on the need to promote positive, healthy, and satisfactory relationships, as well as raising awareness of this need among all professionals responsible for people's health.

Conflicts of Interest:
The authors declare no conflict of interest.