Currently, the rising prevalence of mental health problems among adolescents worldwide is a growing concern and indicates a trend toward younger age cohorts ^[1][2][3][4][1,2,3,4]. According to statistics released by the World Health Organization, approximately one in every seven adolescents between the ages of 10 and 19 suffers from mental health problems [5]. A recent meta-analysis study of 96,000 adolescents from 11 countries found that almost 90% of the 21 studies covering 23 indicators of anxiety, depression and general mental health exhibited an upward trend. This suggests a significant escalation in the severity of negative emotions and mental health problems among adolescents [6]. Specifically, a national social survey conducted in Iceland found that between 2016 and 2020, the proportion of 13-year-old Icelandic adolescents with depression symptoms increased from 16.52% to 18.72%, while mental well-being decreased from 25.21% to 23.13% [1]. Some studies have also highlighted the exacerbation of adolescent mental health problems due to prolonged home confinement and deteriorating family dynamics during the COVID-19 pandemic [7]. For instance, the prevalence of depression and anxiety symptoms in Chinese adolescents increased significantly from 36.6% to 57.0% and from 19% to 36.7%, respectively, leading to a significant increase in the risk of emotional dysregulation [8].

Conscientiousness serves as a protective factor in mitigating the impact of negative emotions on adolescents. Adolescents with high levels of conscientiousness are more likely to exhibit positive psychological traits, such as emotional stability, self-management skills and effective coping strategies ^{[9][10][11][12]}[11,16,17,18]. Conversely, neuroticism has long-term detrimental effects on individual development, including reduced quality of life, poorer health, increased frequency of experiencing unpleasant events and a potentially shortened life span. Individuals with higher levels of neuroticism are more likely to experience negative emotions, show symptoms of depression and anxiety, and suffer from mental health problems ^{[13][14][15][16][17]}[19,20,21,22,23]. Therefore, there is an urgent need to identify the key factors for preventing the exacerbation of neuroticism in adolescents and fostering conscientiousness development to effectively reduce the occurrence of negative emotions, promote adolescent mental health and facilitate holistic development.

It is worth noting that adolescence is a critical period for individual development and personality formation ^{[3][4][9][18]}[3,4,11,24], where the parent‒child relationship is considered a key factor, which may influence adolescent development and mental health ^{[19][20][21][22]}[25,26,27,28]. The parent‒child relationship encompasses the emotional, communicative and interactive aspects between children and their parents. The ecological systems theory posits that parents are not only the earliest socializing agents for individuals but also play a crucial role in the microsystem of the family ^[23][29]. In China in particular, early attachment formation is influenced by long-standing family-oriented values. The impact of the parent‒child relationships formed by the emphasis on shared parenting in everyday life cannot be overlooked in individual development. According to the stress-buffering model, social support or positive relationships with others can mitigate the potentially detrimental impacts of stressful events ^[24][30]. In the context of the family environment, the support and warmth derived from close parent‒child relationships may help alleviate the stress, which adolescents encounter in school or peer relationships. However, further empirical research is necessary to validate these assumptions. Previous research has focused on the influence of parent‒child relationships on adolescent aggression, maladaptive behaviors, social–emotional difficulties and general levels of mental health ^{[25][26][27][28]}[31,32,33,34], but specific investigations of their effects on the development of conscientiousness and neuroticism are lacking. In reality, early adolescence marks a critical juncture characterized by physiological changes, academic adjustment and peer pressure, leading to crises and an urgent need for attention in parent‒child relationships ^[29][9]. On the one hand, as individuals in adolescence increasingly yearn for independence and seek autonomy, attachment to parents diminishes with age, resulting in more arguments and fewer opportunities for parent‒child communication ^{[10][11][27][30]}[16,17,33,35]. On the other hand, in countries such as China, with limited educational resources and intense competition, parents have high expectations for their children’s education and often demand outstanding academic performance, which puts enormous pressure on children ^[31][32][36,37] and hinders the establishment of harmonious parent‒child relationships. Similarly, in the case of Bangladeshi middle school students, a mixed-methods study reveals that parents willingly bear significant financial burdens to enroll their children in extracurricular tutoring in order to enhance academic competitiveness. This places considerable demand on the students, who have to cope with a heavy academic workload even in their leisure time, sacrificing adequate rest and leading to profound psychological stress ^[33][38]. A study of Canadian adolescents further found that parent–child relationships tend to become rigid, especially when parents impose unrealistic educational expectations, increasing students’ vulnerability to self-injury behaviors ^[34][39]. The evidence from German fifth graders suggests that positive parent–child relationships and parental understanding of real needs are essential prerequisites for promoting children’s psychological well-being ^[35][40]. Therefore, it is important to understand the current status of parent‒child relationships among middle school students and their role in the development of conscientiousness and neuroticism.

2. Parent‒Child Relationship and Neuroticism

Previous literature has extensively discussed the influence of parent‒child relationships on adolescent neuroticism, but there is little evidence on the influence of neuroticism on parent‒child relationships. In an autobiographical review of the risk factors for depression, Hammen (2018) suggests that experiences of rejection, exclusion and conflict in interpersonal relationships, particularly parent‒child relationships, can shape negative cognitive patterns and self-evaluations, leading to higher levels of depression risk ^[36][42]. Warm parent‒child relationships can act as a protective factor against the negative effects of stress ^[37][43]. Meanwhile, some empirical studies have focused on the relationship between parent‒child relationships and adolescent mental health, particularly negative emotional traits, but most of them have found only correlational relationships. For instance, Li et al. (2020) used cross-sectional data to show a positive correlation between improved parent‒child relationships and better mental health among Chinese middle school students ^[27][33]. A study involving 234 British adolescents aged approximately 18 found a significant negative correlation between parent‒child relationships and adolescent neuroticism ^[38][44]. Another study of public high school students in New York revealed that a lack of intimacy with parents was associated with a higher degree of depressive mood ^[39][45]. The evidence from a study of 847 Israeli adolescents showed that adolescents with more intimate parental relationships experienced less distress, higher levels of happiness and more social support ^[22][28]. In addition, previous literature has analyzed the unidirectional predictive relationship between parent‒child relationships and neuroticism. For example, a longitudinal study of nearly 700 adolescents from New Jersey and Colorado found that high levels of parent‒child bonding (i.e., closer parent‒child relationships) could protect adolescents from the negative effects of peer stressors and reduce depressive symptoms ^[29][9]. A survey of 290 European–American adolescents found that warm parental behaviors significantly predicted an increase in adolescent optimism and a decrease in neuroticism levels ^[19][25]. A one-year longitudinal study involving a sample of 418 participants found that the quality of parent‒child relationships in eighth grade significantly predicted depressive mood in ninth grade ^[40][46]. However, these studies have limitations, such as insufficient representativeness of the sample and lack of generalizability of the conclusions ^[38][44]. As mentioned earlier, given the importance of measuring the quality of parent‒child relationships, it is necessary to examine the bidirectional relationship between the closeness level of parent‒child relationships and adolescent neuroticism. Unfortunately, previous research has rarely investigated the dynamic relationship between these two variables over time, and in particular, empirical evidence on the influence of neuroticism on parent‒child relationships is lacking ^[10][16]. This is the gap, which the current study aims to address and analyze.

3. Parent‒Child Relationships and Conscientiousness

There is currently limited direct research on the bidirectional relationship between parent‒child relationships and conscientiousness development, although most of the literature suggests a potential positive correlation between these two variables. For example, a survey of nearly 1000 Chinese primary school students confirmed the role of family environmental factors in shaping conscientiousness, revealing a significant positive correlation between parent‒child relationships and children’s levels of conscientiousness ^[41][47]. Another study of some 750 people in the community also found a significant positive correlation between parent‒child relationships and conscientiousness, with respondents reporting lower scores in conscientiousness among those who reported lower levels of parental care and higher levels of parental intrusiveness ^[42][48]. As an essential component of the family ecological environment, the parent‒child relationship has a positive impact on individual adjustment. Compared with unhealthy and negative parent‒child relationships, close and positive parent‒child relationships can facilitate the development of individual adaptive abilities ^[29][9]. Additionally, some studies have examined the association between parental nurturing behaviors, family environmental characteristics and adolescent conscientiousness, reflecting to some extent how positive parent‒child relationships contribute to the development of adolescent conscientiousness. A survey conducted among 674 participants aged 18 to 28 from three universities in Slovenia revealed a negative correlation between conscientiousness and perceived parental intrusiveness and fear of disappointment from mothers, suggesting that individuals with lower levels of conscientiousness may have poorer relationships with their parents ^[10][16]. Studies conducted in Serbia and Germany found a positive correlation between adult conscientiousness and a supportive family environment in childhood ^[12][18]. A survey of 402 adolescents aged 14 to 21 found significant positive correlations between conscientiousness (including resilience) and both mother support and father support ^[43][49]. Although a study of 287 Dutch families also found an association between the quality of the parent‒child relationship and conscientiousness, the association was relatively weak ^[44][50]. Furthermore, a meta-analysis conducted by Prinzie et al. (2009) found that higher levels of conscientiousness and lower levels of neuroticism in parents were associated with greater warmth and behavioral control, while lower levels of neuroticism were associated with greater autonomy support. However, it is important to note that focused on parents as subjects, whereas in reality, as the recipients of education, children’s personality traits and their development also deserve attention ^[21][27]. In summary, there is currently a lack of literature based on longitudinal data, which reveals the bidirectional relationship between parent‒child relationships and conscientiousness, and empirical analysis is needed to provide new evidence. The existing research mainly focuses on Western countries and includes a wide age range, making it difficult to directly apply the conclusions to the adolescent population in the Chinese context.