Lonely in the Dark: Trauma Memory and Sex-Specific Dysregulation of Amygdala Reactivity to Fear Signals

Let me in: The neural correlates of inclusion motivation in loneliness

BACKGROUND

While it is well-established that humans possess an innate need for social belonging, the neural mechanisms underlying motivation for connection are still largely unknown. We propose that inclusion motivation - measured through the effort that individuals are willing to invest to be included in social interactions - may serve as one of the basic building blocks of social behavior and may change in lonely individuals.

METHODS

Following the screening of 303 participants, we scanned 30 low- and 28 high-loneliness individuals with functional magnetic resonance imaging while they performed the Active Inclusion Task (AIT). The AIT assesses the participants' levels of effort invested in influencing their inclusion during classic Cyberball conditions of fair play and exclusion.

RESULTS

High- compared to low-loneliness individuals showed higher urgency for inclusion, specifically during fair play, which correlated with higher activity in the right thalamus. Furthermore, in high-loneliness individuals, we found increased functional connectivity between the thalamus and the temporoparietal junction, putamen, and insula.

LIMITATIONS

Participants interacted with computerized avatars, reducing ecological validity. Additionally, although increasing inclusion in the task required action, the physical demand was not high. Additional limitations are discussed.

CONCLUSIONS

Inclusion motivation in loneliness is heightened during fair but not exclusionary interactions, and is linked to activity in brain regions implicated in appetitive behavior and social cognition. The findings indicate that lonely individuals may view threat in inclusionary interactions, prompting them to take action to regain connection. This suggests that inclusion motivation may help explain social difficulties in loneliness.

Homeostatic Regulation of Energetic Arousal During Acute Social Isolation: Evidence From the Lab and the Field

Recent evidence suggests that social contact is a basic need governed by a social homeostatic system. Little is known, however, about how conditions of altered social homeostasis affect human psychology and physiology. Here, we investigated the effects of 8 hr of social isolation on psychological and physiological variables and compared this with 8 hr of food deprivation in a lab experiment (N = 30 adult women). Social isolation led to lowered self-reported energetic arousal and heightened fatigue, comparable with food deprivation. To test whether these findings would extend to a real-life setting, we conducted a preregistered field study during a COVID-19 lockdown (N = 87 adults; 47 women). The drop in energetic arousal after social isolation observed in the lab replicated in the field study for participants who lived alone or reported high sociability, suggesting that lowered energy could be part of a homeostatic response to the lack of social contact.

Loneliness and diurnal cortisol levels during COVID-19 lockdown: the roles of living situation, relationship status and relationship quality

Loneliness and social isolation have become increasing concerns during COVID-19 lockdown through neuroendocrine stress-reactions, physical and mental health problems. We investigated living situation, relationship status and quality as potential moderators for trait and state loneliness and salivary cortisol levels (hormonal stress-responses) in healthy adults during the first lockdown in Germany. N = 1242 participants (mean age = 36.32, 78% female) filled out an online questionnaire on demographics, trait loneliness and relationship quality. Next, N = 247 (mean age = 32.6, 70% female) completed ecological momentary assessment (EMA), collecting twelve saliva samples on 2 days and simultaneously reporting their momentary loneliness levels. Divorced/widowed showed highest trait loneliness, followed by singles and partnerships. The latter displayed lower momentary loneliness and cortisol levels compared to singles. Relationship satisfaction significantly reduced loneliness levels in participants with a partner and those who were living apart from their partner reported loneliness levels similar to singles living alone. Living alone was associated with higher loneliness levels. Hierarchical linear models revealed a significant cross-level interaction between relationship status and momentary loneliness in predicting cortisol. The results imply that widowhood, being single, living alone and low relationship quality represent risk factors for loneliness and having a partner buffers neuroendocrine stress responses during lockdown.