Neurogenetics and Epigenetics 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.