Despite increasing incidence across the world, not much evidence is available for understanding and effective management of loneliness. More recently, the COVID-19 pandemic, hard economic times, parental stress, marriage issues and other factors pressed the global population with severe loneliness in high-income, low and middle-income countries (LMICs). This literature review investigates the current landscape of loneliness in high and LMICs to identify new developments, knowledge gaps and insights. This literature search in electronic databases, PubMed/Medline and Google Scholar, to gather qualitative and quantitative evidence and evaluate reported symptoms, prevalence and variance of loneliness across populations. The review focused on unaddressed or contentious issues that are vital for evidence-based interventions. The incidence of loneliness among adolescents, married, children, and separated partners in high and LMIC resonated around vulnerability due to socio-economic, cultural, political and ethnic features. A global incidence of loneliness manifested through parental stress, family conflict, abuse and victimization, racial discrimination, loss of jobs, the COVID-19 pandemic and weak social connections. In children aged 4 to 10 years, loss of pro-social activities like hobbies, sports, school, family conflicts, child-parent disagreements, sedentary behaviors like increased screen time, health disparities and racism have been associated with loneliness. Loneliness has been deemed a trigger of poor social development, quality of life and family fragmentation. The global variance of loneliness can be attributed to unique risk factors. Loneliness implicates social isolation, stress, anxiety, and sleep disturbances among children, adolescents and elderly people. Apart from parental stress, the recent pandemic amplified its prevalence due to hard economic times, loss of jobs and curfews. Males, adolescents and children are the major victims of ensuing loneliness. nonetheless, our study established that physical exercise is an effective intervention against loneliness. Keywords: Loneliness Research, Social Isolation, Mental Health, Psychological Well-being, Current Perspectives