The Psychological and Cognitive Effects of Loneliness and Social Isolation: A Primer for Clinicians

Introduction

Humans are a social species by nature, and social connectedness is vital for health and well-being. Loneliness and social isolation are two important facets of social disconnection, which has been associated with myriad adverse health outcomes (National Academy of Sciences, Engineering, and Medicine [NASEM], 2020). Loneliness, an aversive psychological experience, refers to the subjective feeling of being isolated, and arises from a discrepancy between desired versus actual levels of social connection (McKenna-Plumley et al., 2023; NASEM, 2020; World Health Organization [WHO], 2025). Loneliness occurs as the result of too few social connections, insufficient support from those connections, or low-quality interactions (WHO, 2025). Social isolation is defined as an objective lack of roles, relationships, or contacts with others (NASEM, 2020; WHO, 2025). 

According to a recent Centers for Disease Control (CDC) report using data collected from 26 U.S. states, the overall prevalence of loneliness was 32.1%, with the highest rates reported in individuals aged 18-34 (43.3%) and with declining rates reported over age groups (Bruss et al., 2024). Another study using global data from 9 longitudinal studies encompassing 128,118 participants showed that loneliness follows a U-shaped curve, heightened during childhood, decreasing until approximately age 50, then increasing into older adulthood (Graham et al., 2024). In addition to varying with age, rates of loneliness are higher in those with less than a high school education (41.1%), those who were never married (45.9%), those with household incomes below $25,000 (47.9%), and in women compared to men (33.5% versus 30.7%; Bruss et al., 2024). Rates of social disconnection are also likely to be higher in marginalized groups such as people with disabilities, those in the LGBTQ or questioning community, migrants and refugees, and ethnic minorities or indigenous people (WHO, 2025, Bruss et al., 2024). In 2023, the United States Surgeon General declared social isolation and loneliness an epidemic (Office of the Surgeon General [OSG], 2023). While significantly heightened rates of loneliness were reported during the Covid-19 pandemic, a meta-analytic study found that the effect size was small (Ernst et al., 2022), highlighting the chronicity of the problem. 

The Surgeon General’s advisory warned of the individual and societal costs of isolation and loneliness, citing detrimental effects on physical, cognitive, and psychological health (OSG, 2023). Epidemiological studies illuminating trends in loneliness across the lifespan underscore the need for both preventative and remedial interventions, which will only become more important as the number of Americans aged 65 and older increases to a projected 82 million by 2050 (Vespa et al., 2020). Here, we detail the adverse effects of social disconnection on psychological and cognitive health, describe mechanisms by which these effects occur, and discuss clinical applications.  

Impact of Social Disconnection on Psychological Functioning

The psychological effects of social disconnection are far-reaching. In a meta-analysis investigating the relationship between loneliness and new onset mental health problems, a pooled adjusted odds ratio of 2.33 (95% confidence interval [CI] 1.62-3.34) for risk of new onset depression in adults who are often lonely compared to those who are not was reported (Mann et al., 2022). Positive associations for anxiety and suicidal ideation/self-harm were also found. Cross-sectional data from a large U.S.-based study showed adjusted prevalence ratios for stress and history of depression to be 3.61 and 2.38, respectively, for lonely compared to non-lonely adults (Bruss et al., 2024). Social disconnection has also been associated with social anxiety and psychosis (Michalska da Rocha et al., 2018 Teo et al., 2013).

Impact of Social Disconnection on Cognitive Functioning

A number of studies have shown associations between social isolation and loneliness on individual cognitive functions such as memory, processing speed, attention, and verbal fluency (see Cardona and Andres, 2023 for review). A meta-analysis using longitudinal data from more than 600,000 individuals showed that loneliness increased risk for all-cause dementia (hazard ratio [HR] 1.306, CI 1.197-1.426), dementia due to Alzheimer’s disease (HR 1.393, CI 1.290-1.504), vascular dementia (HR 1.735, CI 1.483-2.209), and cognitive impairment not dementia (HR 1.150, CI 1.113-1.189; Luchetti et al., 2024). Other studies have also demonstrated increased risk for mild cognitive impairment and/or dementia in those who are socially isolated (Lara et al., 2019; Qiao et al., 2022, Salinas et al., 2022), and recent work has suggested that loneliness and social isolation may contribute to faster rates of cognitive decline in dementia (Myers et al., 2025). Interestingly, research has also suggested a possibly protective effect of socialization on cognition. The Northwestern University SuperAging Program (Weintraub et al., 2025) defined “superagers” as persons > 80 years old who obtained delayed word recall scores at least equal to those of individuals 20-30 years younger. Superagers had fewer Alzheimer’s disease-type changes in the brain among other neurobiological differences compared to age-matched cognitively average peers, differences which were not explained by lifestyle factors. Superagers were described as sociable and gregarious. They relished extracurricular activities, rated relationships with others more positively, and tended to endorse higher levels of extraversion than their peers, raising the possibility that social connection played an important role in protecting against cognitive decline in this group.

Mechanisms

Humans are social beings with complex social cognition who suffer stress when lonely and isolated (Finley and Schaefer, 2022). When the intrinsic need for connection is not met, it can trigger harmful psychological and biological reactions. For example, loneliness can foster feelings of hostility, decreased interpersonal trust, pessimism, anxiety, and low self-esteem (Hawkley et al., 2010; Finley and Schaefer, 2022). As summarized by Finley and Schaefer (2022), loneliness fosters vigilance towards social threat, increased propensity to mislabel emotions as negative, faster identification of negative emotional faces, decreased functional MRI (fMRI) activity in regions important for emotional processing such as the amygdala and nucleus accumbens during a trust compared to a risk game, and fMRI evidence of connectivity shifts in the default (associated with daydreaming) and limbic networks (important for emotional processing). Such psychobiological changes can result in a feedback loop leading to increased disconnectedness and risk for mental health disorders. 

Loneliness can also trigger a chronic stress response, leading to hyperactivity of the hypothalamic pituitary axis (HPA). The associated prolonged release of cortisol increases inflammation, oxidative stress, and total peripheral resistance. These changes can result in elevated blood pressure in middle to older adulthood, can disrupt neural systems, and can induce cell death throughout the body (Finley and Schaefer, 2022), possibly contributing to cognitive impairment. Chronic stress also causes hypervigilance, contributes to lack of sleep, diminishes self-regulation of health behaviors such as exercise, and increases susceptibility to depression and anxiety by inducing slowing in brain regions that influence emotion, factors which can also contribute to cognitive impairment (Finley and Schaefer, 2022; Hawkley et al., 2010). 

Finally, loneliness has been associated with gray matter loss in the brain, which contributes to mild cognitive impairment (MCI) and dementia (Dabiri et al., 2024). Contrastingly, social connectedness promotes oxytocin release which fosters positive emotion (Viswanathan and Carey, 2025). Connectedness creates greater opportunity for interaction with others, increased cognitive activity, and the potential for greater exposure to novelty, contributing to cognitive reserve and potentially to better cognitive outcomes as people age. Finally, social connection may lead to earlier detection of emerging cognitive impairment and more prompt intervention, possibly slowing the progression of disease. Improved neuropsychiatric functioning and reduced caregiver burden could be effects of early intervention, increasing the likelihood of remaining connected versus becoming isolated. 

Clinical Applications

 Assessment

The far-reaching effects of social disconnection on psychological and cognitive health highlight the importance of careful assessment and intervention to prevent, reverse, or ameliorate its effects. Such a focus may be particularly important when working with patients closer to either pole of the age spectrum given the U-shaped curve that loneliness follows, but attention to these concepts throughout the lifespan is recommended. Clinicians are encouraged to incorporate questions assessing loneliness and social isolation as a standard part of the initial clinical interview and to assess social connectedness periodically throughout the course of treatment. Various lines of questioning are recommended, including inquiry about routines, leisure or volunteer activities, participation in religious or community-based activities, time spent with friends or family, workplace relationships, and club or group membership. Assessing quality of relationships with others in addition to quantity is paramount, as is determining whether a distressing discrepancy exists between desired versus actual social contact. A variety of scales can be used to measure social connectedness (see NASEM, 2020 for examples). These scales can be used for initial assessment and to measure the impact of interventions aimed at social connection.   

Intervention

After identifying an individual as lonely or socially isolated (or at increased risk for social disconnection), adopting a patient-centered approach to intervention that aligns with the individual’s ideals and values is recommended. Patient-centered approaches help the clinician and patient form an unbiased treatment plan, with a shift away from conceptualizing the patient as a “sufferer” and making the individual a care partner (Eklund et al., 2019). A patient-centered approach is further recommended, as there may be increased incentive or motivation to achieve the identified goals (Welch et al., 2024). The Department of Veterans Affairs Whole Health approach is an example of a patient-centered care model and provides an excellent framework with publicly available and useful graphic depictions, web-based tools, and handouts that can be used in treatment with both civilian and veteran patients (see va.gov/wholehealth). Once goals have been identified, interventions aimed at increasing social connection and decreasing loneliness can be devised. Approaches to increasing social connectedness can include helping an individual identify and change maladaptive patterns of thinking, providing psychoeducation on the harmful effects of loneliness and social isolation, identifying opportunities for supported socialization, and adopting wider community-based approaches (Mann et al., 2017). Decreased screen time if much of one’s time is spent browsing on devices such as computers, phones, or tablets; exploration of the individual’s interests/hobbies and any associated community activities, organizations, or groups; and devising a plan for gradual integration with others can be targets of treatment. Group therapy might also be considered. Research has shown that interventions directed at reducing loneliness are generally effective, particularly those that combine approaches and objectives (Patil and Braun, 2024). Such endeavors should be devised taking into account resources and barriers that might affect one’s ability to participate. Lifestyle changes are important for sustained intervention effectiveness (Morrish et al., 2023). Thus, having an ongoing focus on social connection in treatment is recommended, though treatment needs may vary with age given the U-shaped curve that loneliness follows.

 Conclusion

Social connection is a basic human need, yet approximately 32% of Americans report loneliness. Rates of loneliness vary based on age and other demographic and social factors and are known to differentially affect the young and old, women, and persons in disadvantaged or marginalized groups. The absence of social connection can trigger a variety of psychological and biological mechanisms that increase risk for depression, anxiety, stress, and cognitive impairment/dementia. The deleterious and potentially self-perpetuating psychological, medical, and cognitive consequences of social disconnection are preventable or changeable via acknowledgement of the problem, careful assessment, and intervention. Mental health providers, with their regular and ongoing interactions with individuals seeking care, are uniquely positioned to play an important part in ending the social disconnection epidemic and are called to intervene on this global health priority.