1. Introduction

Loneliness has been increasingly recognized as a significant psychological factor that mediates the relationship between the quality of interpersonal relationships and overall well-being. This mediating role becomes particularly crucial when examining how relationship quality impacts well-being across different life stages. Previous research has shown that loneliness can have negative effects on mental health. It can also reduce life satisfaction and affect the overall stability of romantic partnerships. However, much of the existing literature mainly focuses on specific life stages. It often overlooks the broader effects of loneliness that span across different ages. Understanding how loneliness interacts with relationship quality in various age groups is essential. It is important to create comprehensive strategies to reduce its harmful effects on well-being and romantic satisfaction.

This literature review focuses on two review questions that try to fill gaps in existing research. The first question examines how loneliness acts as a mediator between relationship quality and well-being across different stages of life. These stages include adolescence, young adulthood and middle age. By looking at how this mediation works in various age groups, the review highlights how loneliness changes and affects relationships and well-being throughout a person’s life. The second question explores how the fear of being single (FOBS) influences relationship quality and well-being, especially in young adults. This question explains why some young people may avoid getting into romantic relationships due to feelings of loneliness. It also looks at how this fear can impact their overall well-being. Additionally, the review discusses which interventions can effectively reduce loneliness, addressing the need for strategies that improve mental health and satisfaction in relationships.

The integration of existing literature on these topics provides a comprehensive understanding of how loneliness impacts romantic relationships and well-being across different stages of life.

This review not only compiles current knowledge but also lays the groundwork for future research in this field. Through identifying the key factors that contribute to loneliness and suggesting possible interventions, this literature review can help those who want to explore and understand the complex links between loneliness, romantic relationships and well-being.

2. What’s loneliness?

Loneliness is a multifaceted and highly subjective experience that has attracted the attention of scholars from various academic fields. These studies have provided important insights into its complicated nature. Loneliness is not simply about being by oneself or lacking social interaction. Instead, it is a distressing emotional experience. This distress comes from the gap between the social relationships a person wants and those they actually have [1]. This definition suggests that loneliness can occur regardless of a person’s social situation. It is more closely related to the emotional satisfaction one gets from social connections than to how often these interactions happen.

Weiss and Sullivan, as discussed in recent studies, explain that loneliness can be an emotional reaction. This reaction occurs when someone feels they lack the social connections and intimacy they need. This idea suggests that loneliness is not about simply being alone. Rather, it is about feeling lonely and unsupported in the social environment. It reflects a large gap between the relationships one currently has and the relationships one wishes to have [2].

The subjective nature of loneliness is highlighted even more when these studies compare it to physical solitude. Loneliness is marked by a person’s dissatisfaction with the quality of communication and emotional connection in their social relationships. This suggests that just being around others does not solve the problem of loneliness if those interactions do not have depth and emotional importance [3].

Moreover, loneliness is not just a desire for more social contact. It also involves a need for more meaningful and satisfying social interactions. The core of loneliness is a qualitative judgment of one’s social interactions—how deep, intimate, and emotionally fulfilling they are. This perspective shows that simply increasing the number of social contacts without improving their quality is not likely to reduce feelings of loneliness.

2.1. Review Question_1: The Mediating Role of Loneliness in the Relationship Between Relationship Quality and Well-being Across Different Life Stages

Loneliness has been identified as a critical factor in the relationship between relationship quality and well-being across various life stages, with its influence varying based on age and life circumstances. This section explores the impact of loneliness on well-being and relationship quality among three distinct age groups: adolescents, young adults and middle-aged married individuals.

In adolescence team, loneliness is often linked to the development of identity and social connections. Adolescents, particularly those around 15 years old, are at a critical juncture where peer relationships become increasingly important. The study by Goodfellow and Wolfe in Nordic countries reveals that loneliness among 15-year-olds significantly correlates with lower mental well-being and self-esteem[2]. Adolescents are acutely sensitive to their social environment, and the failure to establish meaningful connections can lead to persistent feelings of loneliness. This loneliness not only directly affects their mental health but also exacerbates the effects of poor relationship quality, leading to a downward spiral in well-being. The high prevalence of loneliness among adolescents in Finland and Iceland, where 19.2% and 17.1% respectively reported frequent loneliness, underscores the importance of addressing these feelings early to prevent long-term psychological issues [2].

As individuals transition into young adulthood, the focus shifts to the formation and maintenance of romantic relationships. During this period, loneliness continues to mediate the relationship between relationship quality and well-being but with a different emphasis. The study by Givertz et al. highlights that young adult, aged 16 to 24, who have insecure attachment orientations are particularly prone to loneliness, especially when their romantic relationships are unsatisfactory[4]. Different with adolescents, whose loneliness is more often related to peer interactions, young adults experience loneliness more intensely within the context of romantic relationships. This kind of loneliness, which is made worse by a fear of being single (FOBS), often causes people to stay in relationships that are not satisfying. This situation creates a cycle of poor relationship quality and declining well-being. The psychological distress that comes with this kind of loneliness can have long-term effects on life satisfaction and mental health. This indicates the need for targeted interventions that address the specific relationship challenges that people face at this stage of life[4].

In middle age, the nature of loneliness changes once again. It is often linked with major life transitions, such as when children leave home or when retirement begins. Lyyra et al.’s study explore how loneliness impacts married people who are in their middle age[5]. Their study shows that even those in stable marriages can feel lonely if there is a lack of emotional intimacy. Unlike the more intense and outwardly focused loneliness that is common in adolescence and young adulthood, loneliness in middle age is often more subtle. It can slowly creep into even well-established relationships. This lack of emotional connection can cause marital satisfaction to decrease. It can also lead to a significant decline in overall well-being. The loneliness that people experience at this stage is not just about not having relationships. It is more about the quality and the depth of the relationships they already have. This makes it a critical factor for understanding the broader impact of relationship quality on mental health[5].

When comparing these different stages of life, it becomes clear that loneliness consistently acts as a mediator in the relationship between relationship quality and well-being. However, its forms and effects are different in each stage. In adolescence, loneliness is mainly caused by the failure to form strong peer connections. This directly impacts mental health and overall well-being. In young adulthood, loneliness is more closely linked to romantic relationships. The fear of being single makes its effects worse, leading to ongoing emotional distress. As people reach middle age, loneliness becomes more closely tied to the quality of existing relationships. In particular, emotional intimacy or lack, within marriage plays a crucial role in determining a person's happiness.

These developmental differences show the changing nature of loneliness as people move through different stages of life. As individuals grow older, the sources of loneliness, as well as its effects, also change. However, its role as a mediator between the quality of relationships and overall well-being stays the same. To effectively address loneliness at each of these stages, it is necessary to use tailored approaches that consider the specific challenges and needs that each age group faces. Adolescents need support to help them build strong and meaningful connections with their peers. Young adults, on the other hand, require interventions that focus on the complexities of romantic relationships and attachment issues. Meanwhile, middle-aged individuals benefit most from strategies that aim to enhance emotional intimacy in long-term relationships.

2.2. Review Question_2: The Role of Fear of Being Single in Mediating the Effects of Relationship Quality on Loneliness and Well-being Among Young Adults

As mentioned in the first review question, the fear of being single (FOBS) is a psychological factor that is being recognized more and more. It can have a significant impact on a person’s emotional well-being, especially in romantic relationships. This fear is defined as the worry, anxiety, or distress about not having a romantic partner. Research has shown that FOBS can have strong effects on loneliness and overall well-being, especially among young adults. The fear of being single often mediates the connection between the quality of a relationship and levels of loneliness and well-being. It intensifies the negative impacts of poor relationship quality on mental health [6]. This section examines the role of FOBS in this mediation process by drawing on recent studies to clarify the complex dynamics at play.

The study by Adamczyk offers valuable insights into how the fear of being single affects the link between relationship quality and loneliness in young adults [6]. The research indicates that young adults who have a high level of fear about being single are more likely to experience feelings of romantic loneliness. This is especially true when they are in unsatisfying relationships or when they are not in a relationship at all. This fear worsens feelings of loneliness by increasing people's awareness of the perceived deficiencies in their social and romantic lives. Adamczyk's study also suggests that FOBS can reduce an individual’s overall sense of well-being. Individuals who fear being single may remain in unsatisfying relationships to avoid feeling lonely, which creates a cycle of poor relationship quality and heightened loneliness [6].

FOBS can also push individuals to value having a relationship more than the quality of that relationship. This is particularly common among young adults. Because they are afraid of being single, they might choose to enter or stay in relationships that are not emotionally satisfying or could even be harmful. The study by Spielmann et al., as mentioned in Adamczyk's research, supports this idea[7]. It shows that people who have a fear of being single often lower their standards when it comes to relationships. This can lead to less satisfaction in the relationship and more loneliness. Thus, the fear of being single acts as a factor that worsens the negative effects of poor relationship quality on both loneliness and overall well-being[7].

Besides its direct impact on how people choose relationships, the fear of being single also interacts with unmet needs for belonging. This interaction further affects how relationship quality impacts loneliness. According to Adamczyk’s study, individuals who are afraid of being single often experience a stronger unmet need to belong[6]. This unmet need makes them feel even lonelier when they are not in a relationship or when the relationship they are in does not meet their emotional needs. The combination of an unmet need for belonging and the fear of being single creates a strong mediating effect that can significantly damage a person's well-being. The study suggests that in order to improve the well-being of people who suffer from loneliness in romantic relationships, it is crucial to address both the fear of being single and the unmet needs for belonging.

Girme et al.’s research also make important contributions to understanding of how the fear FOBS affects the link between relationship quality and well-being[8]. Their study finds that people who have strong approach-related social motivations to those who actively look for and value social connections are particularly vulnerable to the negative impacts of FOBS. When these people feel a fear of being single, they are more likely to feel lonely and dissatisfied with their lives. This is especially true if their current relationships do not meet their emotional needs. This study indicates that the psychological effects of FOBS are not the same for everyone. They depend on how much a person is motivated by the desire for social connections, which makes the relationship between relationship quality, loneliness, and well-being more complex [8].

Moreover, Girme’s research suggest that FOBS can lead to a cycle of loneliness and poor relationship quality that reinforces itself. Individuals who are afraid of being single may enter or remain in relationships that do not meet their emotional or social needs. However, this only leads to more loneliness and lower life satisfaction. This cycle is difficult to break because the fear of being single can prevent people from leaving unfulfilling relationships, which continues to negatively affect their well-being. The study emphasizes the importance of addressing FOBS to improve relationship quality and reduce loneliness, especially for young adults [8].

2.3. Effective Strategies For Alleviating Loneliness Among Individuals with Mental Health Problems

To effectively reduce loneliness, especially for people who have mental health challenges, several strategies have been recognized as promising. One of the main strategies is to change cognitions through interventions like Cognitive Behavioral Therapy (CBT). This method focuses on targeting the unhelpful cognitive patterns that often come with loneliness. These patterns include negative thoughts about social interactions and a lack of trust in other people. Research has shown that changing these cognitive biases can greatly reduce feelings of loneliness [9].

Another important strategy is social skills training and psychoeducation. These ways aim to improve a person’s ability to interact with others socially. They work by teaching practical skills, such as how to communicate effectively and how to understand social cues. Psychoeducation also provides information on why social relationships are important. This information can help increase a person’s motivation to participate in social activities. Although the full effect of these strategies on loneliness is still being explored, they are crucial for developing the fundamental skills needed to form meaningful connections [9].

Supported socialization is another effective method for reducing loneliness. This approach involves pairing individuals with a supporter who assists them in joining social activities. This kind of support can be particularly important for people who suffer from severe mental health issues. It helps them engage in community activities and build lasting social networks. While the long-term effectiveness of this method can vary from person to person, research has shown that it can reduce social isolation which is a major factor contributing to loneliness [9]

Broader community initiatives, like social prescribing and community development projects also plays an important role. These initiatives are designed to create more inclusive environments. They do this by encouraging people to take part in different community activities, which can naturally help reduce feelings of loneliness. By incorporating these efforts into larger social frameworks, such approaches also help to lessen the stigma that is often associated with loneliness and mental health problems, and they promote a stronger sense of belonging [9].

3. Conclusion

In this literature review, exploring two review questions about the role of loneliness in mediating the relationship between relationship quality and well-being across different life stages. The first review question focused on how loneliness serves as a mediator between relationship quality and well-being, starting from young adulthood and continuing into old age. The findings suggest that loneliness has a significant impact on a person's well-being and this impact changes depending on the stage of life. For instance, in young adulthood the need for close and intimate relationships is very important. When these needs are not met, it often leads to stronger feelings of loneliness which negatively impacts well-being. As people get older, the changes in social roles and relationships, such as retiring or losing loved ones, can make loneliness worse, leading to lower life satisfaction and poorer psychological health.

The second review question examined the role of the FOBS as a mediator in the relationship between relationship quality, loneliness and well-being, especially among young adults. The review showed that FOBS not only affects the decisions people make about their relationships but also increases feelings of loneliness and decreases overall well-being, particularly when the quality of the relationship is low. FOBS can cause people to value being in a relationship more than the quality of the relationship itself. This can result in unsatisfying or even harmful relationships which creates a cycle of loneliness and poor well-being.

Overall, this literature review has shown that the role of loneliness as a mediator in the relationship between relationship quality and well-being is complex. It also changes and develops throughout a person's life. The dynamic nature of loneliness, influenced by changing social roles, life transitions and expectations in relationships, makes it an important factor. It is crucial for understanding the wider effects of relationship quality on psychological health. Loneliness is not just a personal experience but also a social phenomenon that interacts with a person’s social environment and their relationships. This highlights the importance of considering age related factors when studying loneliness and well-being.

In addition, future research could focus on understanding how loneliness mediates the effects of relationship quality across different life stages. Longitudinal studies could offer valuable insights into how loneliness evolves and changes over time. They could also help us to see how relationship quality interacts with other factors, such as mental health and social support, to influence well-being. As loneliness becomes a more frequent issue in aging populations, this trend suggests that research should also pay more attention to older adults. It is essential to explore how interventions can be specifically tailored to address the unique needs of this group.