1. Introduction
Most psychological problems appear in adolescence [1, 2]. Based on the literature spanning the past 20 years, the symptoms of 3%–12% of patients with depression appeared within 14–16 years of age [3]. In the following years, adolescents are expected to be more susceptible to severe depression, anxiety, social dysfunction, academic failure, and even suicidal tendencies [4, 5]. One of the important components that play an essential role in the lives of teenagers is the protection of mental health and wellbeing.
Psychological wellbeing encompasses positive emotions and positive functions [5]. Mental wellbeing includes self-efficacy, objective wellbeing, autonomy and independence, and the ability to recognize other people’s emotions [6]. Psychological wellbeing refers to emotional and cognitive reactions to the perception of personal characteristics and abilities, effective positive interaction with the world, good relationships with the community, and personal growth [7]. It can affect the components of psychological wellbeing, including positive affection, satisfaction with life, and happiness, as well as those of happiness and personal wellbeing, such as self-acceptance, positive relationships, self-regulation, and purpose in life [8]. Family relationships, especially between adolescents and their mothers, are essential to adolescents’ psychological wellbeing.
Among the different factors affecting maternal behaviors include attitudes toward sexual health. Sexual health is a person’s satisfaction with sexual intimacy and ability to create mutual pleasure [9]. The lack of sexual satisfaction weakens marital relationships, for sexual pleasure, allows couples to cope with hardships and problems [10]. In addition to mental and emotional consequences on a person, such as depression and mental, psychological, and personal disorders, dissatisfaction with sexual intimacy will influence other family members, relatives, and social health by leading to aggression, violence, and extramarital affairs [11]. Sexual health is also essential to people’s overall quality of life. For example, better physical and psychological health, overall wellbeing, and quality of life correlate with high intimacy levels [12]. In these conditions, mothers with good sexual relationships with their husbands can experience heightened levels of marital happiness, thereby positively influencing family health, especially that of their adolescent children [1].
Maternal self-differentiation is another factor that affects children’s psychological wellbeing. This trait encompasses acquired intellectual and emotional processing abilities and independence from others. It is the ability to withstand the emotional reactions of others by distinguishing thoughts from emotions [13, 14]. In other words, self-differentiation reflects the driving force that compels an individual to follow its principles, resulting in an independent and distinct identity. In contrast, togetherness is grounded in the impulse to follow the guidelines or orders of others, producing a dependent, interconnected, and unknown identity [15]. People with greater self-differentiation experience more balanced personality development with a sense of togetherness [16].
Attitudes toward sexual health and self-differentiation of mothers can indirectly affect the psychological wellbeing of adolescents through sexual intimacy. Intimacy is one of the most valuable dimensions of human existence and is deemed essential for healthy human functioning. Sexual intimacy involves the sharing and expressing thoughts, feelings, and sexual fantasies with the spouse. This type of intimacy aimed at arousing sexual desire. Sexual intimacy is a complex issue that affects other aspects of couples’ relationships [17]. Sexual intimacy and the resulting satisfaction between couples is the main factor in preventing the breakdown of desires in their sexual behavior. Couples with higher intimacy have the strength to face problems and experience higher marital satisfaction [18]. Numerous studies underscore that marital intimacy affects various factors in family life [19]. Sexual intimacy is the quality of relationships and covers marital intimacy, friendship, and agreement, contributing to a stable and supportive relationship [20]. Donahue et al. reported that experiencing parents’ relationship instability in early childhood is associated with major depression in adolescence [21].
Psychological wellbeing is essential for adolescents’ emotional, psychological, and social functioning. Research has shown that mothers who lack sexual and psychological wellbeing apply interventionist parenting styles when dealing with the behavioral problems of their adolescent children, such as aggression and anti-social behavior. This situation increases the likelihood of behavioral symptoms and problems in children [22]. 
The rationale for this study is highlighted by the lack of simultaneous analysis of the causal model for the psychological wellbeing of adolescents based on attitudes toward sexual health and self-differentiation of mothers when mediated by the sexual intimacy of mothers. Drawing on the presented information, this study seeks to investigate the mediating role of sexual intimacy in the relationships between attitudes toward sexual health and self-differentiation of mothers with the psychological wellbeing of adolescents.

2. Materials and Methods

Study design and participants
Students from Ahvaz senior high schools and their mothers participated in this descriptive-correlational study conducted during the academic year 2021–22. Based on the number of variables and the statistical model, 300 participants were selected for the research sample using the stratified cluster sampling method. Given the number of direct paths, the number of exogenous variables and the number of error variances in path analyses were determined with respect to the number of parameters. Based on Kline’s suggestion, at least 10 participants for each calculated parameter is deemed necessary for testing the model [23]. To ensure sufficient statistical power, nearly 25 participants were allocated for each parameter, resulting a total of 300 participants (10×25+50=300).
In this research, two districts were randomly chosen in Ahvaz City from the educational areas. After that, two high schools for girls and two for boys were chosen. From each school, two classes were randomly selected. Finally, by selecting the research sample, the research questionnaires were provided online to students and their mothers, who were requested to answer the questions. They were assured that their information remained confidential to the researcher. Informed consent of students and their parents was obtained to observe ethical considerations.

Inclusion and exclusion criteria
Participants in the study must be high school students between 16 and 18 years old, provided written consent to participate, and be in good physical or mental health. Participants were excluded if they refused to cooperate with further research and submitted incomplete questionnaires.

Study tools

Psychological wellbeing scale
Ryff’s Psychological Wellbeing Scale [24] includes 18 items, each graded on a 6-point Likert scale from 1 (total disagreement) to 6 (total agreement). Six factors are measured by the tool: Dominance of the environment, independence, personal development, positive interpersonal relationships, life purpose, and confidence. To calculate the questionnaire’s overall score, 6 factors’ scores are added. Hence, the total scores range from 18 to 108. Bayani et al. reported the test-retest reliability coefficient of the scale as 0.82 [25].

Attitude scale toward sexual health 
Designed by Nemcic et al., this scale comprises 50 items distributed across three subscales: Principles of sexual behavior, safe sex, and personal sexual care [26]. The items are scored on a 5-point Likert scale (ranging from 1 for “completely disagree” to 5 for “strongly agree”), with a higher score representing a more positive attitude toward sexual health. This scale’s minimum and maximum scores are 50 and 250, respectively. The maximum and minimum scores are 60 and 12 for the principles of sexual behavior subscale, 14 and 70 for the safe sex subscale, and 24 and 120 for the personal sexual care subscale, respectively. In the present study, the scale’s Cronbach α coefficient was 0.81.

Differentiation of self-inventory
Designed by Skowron and Friedlander, the self-inventory differentiation consists of 45 items developed for measuring people’s self-differentiation [27]. The tool has four subscales: Affective congruency, my status, emotional avoidance, and emotional reactivity. The responses are scored on a 6-point Likert scale ranging from 1 to 6 (“completely agree” to “completely disagree”), with the total score obtained by the summation of all item scores. Ghavibazou et al. reported the reliability coefficient of the scale as 0.84 [28].

The marital intimacy questionnaire
Introduced by Hudson et al. [29], the marital intimacy questionnaire comprises 25 items, each addressing aspects such as “I think that the quality of my sexual life is low or that my husband is not capable of satisfying my sexual needs”). The responses are scored on a 5-point Likert scale (1= for always, 2=for often, 3=for sometimes, 4=for rarely, and 5=for never). Hence, the total score ranges from 25 to 125. Higher scores indicate higher levels of marital intimacy for mothers. The scale’s reliability was reported at 0.77 using the Cronbach α [30].

Data analysis
The Pearson correlation coefficient was used to check the correlation between the study variables. The significance of the mediating relationships was evaluated by the bootstrap method. The structural equation modeling (SEM) technique was used to assess the proposed model in SPSS software, version 27 and AMOS software, version 25.

3. Results
The participants in this study were 300 female and male students, along with their mothers. The average age of female and male students was 16.72±1.64 and 17.23±1.19 years, respectively. The mean age of mothers in this study was 48.81±7.38 years. Regarding gender, 150 participants (50.0%) were female and 150(50.0%) were male students. In terms of mothers’ education, 126(42.0%) had middle school education, 84(28.0%) held diplomas, 75(25.0%) had bachelor’s degrees, and 15(5.0%) had master’s degrees. Moreover, 243(81.0%) were homemakers, and 57(19.0%) were employed. Table 1 presents the descriptive statistics, including Mean±SD, and correlation matrix.



Figure 1 demonstrates the preliminary proposed model for explaining the psychological health of adolescents based on the attitude to sexual health, self-differentiation, and sexual intimacy of mothers.



The root-mean-square error (RMSEA) value of 0.47 indicates that the preliminary model requires modification (Table 2). The chi-square test and other indices could not be computed as they were saturated. After one path was removed (from the self-differentiation of mothers to the psychological wellbeing of adolescents), the model was no longer saturated, allowing the software to compute these indices [31].



In the final model depicted in Figure 2, the RMSEA of 0.04 indicated the model’s good fit.



Table 3 presents path coefficient estimations to assess the direct and indirect paths. The findings revealed no significant relationship between the mother’s self-differentiation and adolescents’ psychological wellbeing (β=-0.05, P=0.293). In contrast, the relationship between mother’s attitudes towards sexual health and adolescents’ psychological wellbeing was positive and significant (β=0.46, P=0.001). The relationship between the mother’s attitude toward sexual health and marital intimacy was positive and significant (β=0.51, P=0.001). Additionally, a positive and significant relationship existed between the mother’s self-differentiation and marital intimacy (β=0.25, P=0.001) and between the mother’s marital intimacy and adolescents’ psychological wellbeing (β=0.47, P=0.001).



According to Table 3, the indirect path of attitude toward the sexual health of mothers to the psychological wellbeing of adolescents was significant when mediated by the sexual intimacy of mothers (P=0.001). The indirect path of the self-differentiation of mothers to the psychological wellbeing of adolescents was also significant when mediated by the sexual intimacy of mothers (P=0.001).

4. Discussion 
The initial finding underscores a direct positive correlation between the attitude toward the sexual health of mothers and the psychological wellbeing of adolescents. The unavailability of similar studies proves the novelty of this study. Beyond its impact on the person’s mental and emotional consequences, such as depression and cognitive, psychological, and personal disorders, dissatisfaction with sexual intimacy will also affect other family members, relatives, and social health by leading to aggression, violence, and extramarital affairs [11]. Unhealthy sexual relationships between parents lead to conflict and incompatibility in their private affairs, thereby affecting their relationships with their children. Hence, the overall affectionate structure of the family is an essential factor in children’s psychological wellbeing. Children in families with parents with healthier relationships can experience greater psychological wellbeing, whereas children in families where parents have conflicts and are incompatible will experience lower psychological wellbeing. The emotional presence of parents, especially mothers, at home and in children’s lives can promote attachment between family members and adolescents’ psychological wellbeing.
There was no significant correlation between mothers’ self-differentiation and adolescents’ psychological wellbeing. This finding is consistent with the research results of previous studies [32]. However, upon scrutiny through SEM, a significant correlation was observed between mothers’ self-differentiation and adolescents’ psychological wellbeing. The entire effect of the self-differentiation variable on the psychological wellbeing of adolescents can be explained through the mediating variable or its indirect correlation. In other words, the self-differentiation of mothers affected the psychological wellbeing of adolescents, albeit indirectly. Self-differentiation indicates that a person has the adequate emotional maturity to communicate with their family without involuntary and emotional reactions in various situations [14]. Self-differentiation is a person’s ability to distinguish intellectual and emotional processes and also covers the ability to experience intimacy with others while preserving independence. Healthy families help their members self-differentiate, enabling them to separate their rational and emotional performance while distinguishing their performance from that of other members.
A positive and direct correlation was identified between the sexual intimacy of mothers and the psychological wellbeing of adolescents, suggesting that improving the sexual intimacy of mothers is expected to enhance the psychological wellbeing of adolescents. It is crucial to consider how specific interactions, functions, and life cycles affect each family member and the entire family when looking at the family system from a systemic point of view. In essence, how parents relate to one another can directly impact their children’s health. Research results from recent studies support this conclusion [19, 21]. Sexual intimacy results from spousal satisfaction and compatibility in different aspects of their life, reinforcing the foundation of the family and ensuring the psychological wellbeing of children to whom this positive sense and attitude are transferred [20]. Typically, sexual intimacy affects many aspects of personal and social life, facilitates parenting, and directly influences the adoption of the right parenting style. Thus, the sexual relationships of parents are essential to their favorability with children and their psychological wellbeing. 
The results also demonstrated that the sexual intimacy of mothers mediated the attitudes toward sexual health and the self-differentiation of mothers with the psychological wellbeing of adolescents. No research was found in the literature to compare the results of this study. The first hypothesis showed a significant correlation between attitude to the sexual health of mothers and the psychological wellbeing of adolescents. Along the indirect path, the attitudes toward the sexual health of mothers promoted sexual intimacy, indirectly improving the psychological wellbeing of children. Meanwhile, there was no significant correlation in the direct relationship between mothers’ self-differentiation and adolescents’ psychological wellbeing. However, indirectly, the self-differentiation of mothers affects the psychological wellbeing of adolescents by first improving the sexual intimacy of mothers. This finding underscores the importance of the self-differentiation of mothers, emotional management, and fair criteria of spouses within the home. A self-differentiator can balance thinking and feeling, show resilience to strong emotions and spontaneity, and has self-control derived from resistance to emotional impulses. Typically, the right approaches to communication, proper family function, and the self-differentiation of the mother to act rationally in different conditions can improve sexual intimacy and the psychological wellbeing of children. Hence, the sexual intimacy of mothers can mediate the relationship of attitudes toward sexual health and the self-differentiation of mothers with the psychological wellbeing of adolescents.

5. Conclusion
The results indicated that the proposed method had a good fit, making an essential step toward recognizing the psychological health factors of adolescents. Furthermore, a positive correlation emerged between the sexual intimacy of mothers and the psychological wellbeing of adolescents. Improving the sexual intimacy of mothers is expected to boost the psychological wellbeing of adolescents. Typically, a proper approach to communication, effective family function, and the self-differentiation of the mother to act rationally in different conditions can improve sexual intimacy and the psychological wellbeing of children. It is recommended to hold workshops to promote effective communication skills and self-differentiation for couples to enhance the sexual intimacy of mothers, thus boosting the psychological wellbeing of adolescents. It is also necessary to emphasize and improve the sexual relationship of parents, which seems to be the most important aspect of marital life. Marital satisfaction ensures that parents have healthy relationships with each other and their children.

Study limitations
Several limitations appeared in the course of this study. Firstly, the statistical population was confined to male and female high school students and their mothers in Ahvaz City. Therefore, it is essential to exercise caution while generalizing the results to students of other grades and cities. For generalization, further studies should be conducted on different samples. Moreover, the non-longitudinal correlational study design and reliance on self-report instruments for data collection call for further research on this topic. 

Ethical Considerations

Compliance with ethical guidelines
The Research Ethics Committee of Ahvaz Branch, Islamic Azad University, approved the present study (Code: IR.IAU.AHVAZ.REC.1401.061).

Funding
This study received no specific support from public, private, or non-profit funding bodies.

Authors contributions
Conceptualization: Hossein Jorfizadeh and Behnam Makvandi; Methodology: Hossein Jorfizadeh and Alireza Heidari; Writing the original draft: Behnam Makvandi and Parviz Asgari; Review and editing: All authors.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgements
The authors express their gratitude to all the students and their mothers who participated in this research.


References