Neurogenetics and Epigenetics of Loneliness

Personality and Psychoneuroimmunology: A Systems Biology Perspective

Research in psychoneuroimmunology (PNI) underscores the intricate connections within the "whole mind-body system." Personality plays a pivotal role, with specific traits linked to stress influencing neural behavior and psychophysiological disorders. Gene expression networks associated with personality affect neuronal plasticity, epigenetic processes, and adaptive behaviors, highlighting the importance of systems biology mechanisms. Systemic inflammation correlates with key personality traits. Understanding the roles of inflammatory and oxidative biomarkers in personality traits and disorders can help identify diagnostic and therapeutic targets for various diseases. Neurobiological features contribute to our understanding of personality disorders and related conditions. Personality traits are linked to distributed neuroendocrine networks, particularly the hypothalamic-pituitary-adrenal (HPA) axis, rather than localized brain areas. Correlations have also been identified between personality traits and thyroid hormones. Disrupted hypothalamic-pituitary-thyroid (HPT) axis functions may be associated with disease severity, depression, and distress, highlighting the need for comprehensive endocrinological and psychopathological evaluations. The gut-brain axis influences personality traits, emotions, stress, and social behaviors. Altered gut microbiota is common in psychiatric conditions, suggesting potential treatments targeting the microbiota. Chronic stress impacts cognitive functions and correlates with personality and mental health, emphasizing the need for comprehensive, multi-dimensional patient profiles for effective prevention and therapy. A biopsychosocial model integrating personality traits will advance personalized and systems medicine.

Effects of maternal separation on punishment-driven risky decision making in adolescence and adulthood

Early life adversity (ELA) is associated with a multitude of neural and behavioral aberrations. To develop treatments to mitigate the effects of ELA, it is critical to determine which aspects of cognition are affected and when these disturbances manifest across the lifespan. Here, we tested the effects of maternal separation, an established rodent model of ELA, on punishment-driven risky decision-making longitudinally in both adolescence (25-55 days old) and adulthood (80-100 days old). Risk-taking was assessed with the Risky Decision-making Task, wherein rats choose between a small, safe reward and a large reward accompanied by an escalating risk of punishment (foot shock). We observed that rats exposed to maternal separation were more prone to risk-taking than controls during adolescence, and demonstrated reduced latency to make both risky and safe decisions. Interestingly, this augmented risk-taking was no longer evident in adulthood. Males and females displayed comparable levels of risk-taking during adolescence then diverged in adulthood, with adult males displaying a sharp increase in risk-taking. Finally, we observed that risk-taking changed across the lifespan in rats exposed to maternal separation, but not in control rats. Collectively, these data reveal that ELA engenders risk-taking in adolescence but not adulthood, and that sex differences in risky decision-making are not evident until adulthood. This has important implications for the development of both behavioral and biological treatments to improve decision-making during the vulnerable adolescent period.

Predicting the Risk of Loneliness in Children and Adolescents: A Machine Learning Study

BACKGROUND

Loneliness is increasingly emerging as a significant public health problem in children and adolescents. Predicting loneliness and finding its risk factors in children and adolescents is lacking and necessary, and would greatly help determine intervention actions.

OBJECTIVE

This study aimed to find appropriate machine learning techniques to predict loneliness and its associated risk factors among schoolchildren.

METHODS

The data were collected from an ongoing prospective puberty cohort that was established in Chongqing, Southwest China. This study used 822 subjects (46.84% boys, age range: 11-16) followed in 2019. Five models, (a) random forest, (b) extreme gradient boosting (XGBoost), (c) logistic regression, (d) neural network, and (e) support vector machine were applied to predict loneliness. A total of 39 indicators were collected and 28 predictors were finally included for prediction after data pre-processing, including demographic, parental relationship, mental health, pubertal development, behaviors, and environmental factors. Model performance was determined by accuracy and AUC. Additionally, random forest and XGBoost were applied to identify the important factors. The XGBoost algorithm with SHAP was also used to interpret the results of our ML model.

RESULTS

All machine learning performed with favorable accuracy. Compared to random forest (AUC: 0.87 (95%CI: 0.80, 0.93)), logistic regression (AUC: 0.80 (95%CI: 0.70, 0.89)), neural network (AUC: 0.80 (95%CI: 0.71, 0.89)), and support vector machine (AUC: 0.79 (95%CI: 0.79, 0.89)), XGBoost algorithm had the highest AUC values 0.87 (95%CI: 0.80, 0.93) in the test set, although the difference was not significant between models. Peer communication, index of general affect, peer alienation, and internet addiction were the top four significant factors of loneliness in children and adolescents.

CONCLUSIONS

The results of this study suggest that machine learning has considerable potential to predict loneliness in children. This may be valuable for the early identification and intervention of loneliness.

Early social isolation disrupts adult personality expression in group-living mites

Animal personalities are characterized by intra-individual consistency and consistent inter-individual variability in behaviour across time and contexts. Personalities abound in animals, ranging from sea anemones to insects, arachnids, birds, fish and primates, yet the pathways mediating personality formation and expression remain elusive. Social conditions during the early postnatal period are known determinants of mean behavioural trait expressions later in life, but their relevance in shaping personality trajectories is unknown. Here, we investigated the consequences of early social isolation on adult personality expression in plant-inhabiting predatory mites Phytoseiulus persimilis. These mites are adapted to live in groups. We hypothesized that transient experience of social isolation early in life, that is, deprivation of any social contact during a sensitive window in the post-hatching phase, has enduring adverse effects on adult personality expression. Newly hatched mites were transiently reared in isolation or in groups and tested as adults for repeatability of various within-group behaviours, such as movement patterns and mutual interactions including sociability, defined as the propensity to associate and interact benignly with conspecifics, and activity patterns when alone. Groups composed of individuals with the same or different early-life experiences were repeatedly videotaped and individual behaviours were automatically analysed using AnimalTA. Social experiences early in life had persistent effects on mean behavioural traits as well as adult personality expression, as measured by intraclass correlation coefficients (indicating repeatability). On average, isolation-reared females moved at higher speeds, meandered less, kept greater distances from others and had fewer immediate neighbours than group-reared females. Group-reared females were highly repeatable in inter-individual distance, moving speed, meandering and area explored, whereas isolation-reared females were repeatable only in the number of immediate neighbours. Activity, quantified as the proportion of time spent moving within groups, was only repeatable in group-reared females, whereas activity, quantified as the proportion of time spent moving when alone, was only repeatable in females reared in isolation. Strikingly, also the early-life experiences of male mates influenced personality expression of mated females, with isolation-reared males boosting the repeatability of behavioural traits of group-reared females. Overall, our study provides evidence that a transient phase of social isolation during a critical period early in life has lasting effects that extend into adulthood, impairing adult personality expression. These effects should cascade upward, changing the phenotypic composition and diversity within populations.

Fostering wellbeing and healthy lifestyles through conviviality and commensality: Underappreciated benefits of the Mediterranean Diet

Among the often-neglected features of healthy diets, such as the Mediterranean diet, is the preparation and sharing of food, which is (or was) done in a social environment governed by social rules rather than by time constraints. The act of eating is a daily human practice that is not limited to meeting nutritional and energy needs but also involves a constructed social dimension of sharing meals that is part of the process of human civilization and food cultures around the world. In this narrative review, we outline the importance of conviviality in steering part of the health effects of healthful diets, with special reference to the Mediterranean diet. Based on the available evidence, we suggest that public health initiatives (such as nudging to promote conviviality) to improve people's eating and living styles, reduce loneliness, and promote the sharing of meals could improve health. Interventions aimed at directly increasing/improving people's social relationships, networking, and conviviality can-directly and indirectly-improve both psychological well-being and general health.

Impact of Intergenerational Shokuiku (Food and Nutrition Education) Programs on Alleviating Loneliness in Japanese Communities across Ages

As loneliness is a risk factor for mental and physical health problems in various age groups, this study aimed to explore the impact of the intergenerational Shokuiku (food and nutrition education) program (IGSP) on loneliness in a Japanese community. This single-arm intervention study conducted between 2022 and 2023 included children (n = 21), guardians (n = 16), university students (n = 3), and older adults (n = 6). The IGSP was a one-day program that included participants making and eating their own bread, butter, and sorbet. Loneliness was measured using the Five-item Loneliness Scale for Children (Five-LSC; Japanese) and the three-item UCLA Loneliness Scale (Japanese; for adults) with other direct questions. Social capital, including civic participation, social cohesion, and reciprocity, was assessed using a self-administered questionnaire. The Five-LSC score significantly decreased post-intervention (p = 0.04). There was a significant increase in adults who reported not feeling lonely (p = 0.001). However, the UCLA Loneliness Scale scores did not show any significant changes. A positive change in social cohesion, including community contribution (p = 0.001) and attachment (p = 0.002), was observed among adults. This study suggests that IGSPs have a positive impact on loneliness in children and a partly positive one in adults. These findings emphasize the potential of intergenerational programs to reduce loneliness in communities.

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.