Loneliness is a current phenomenon that is not only influenced by personal characteristics but also by contextual conditions, resulting in cross-cultural variations in the ways in which we experience and cope with loneliness. This book presents data on loneliness in romantic relationships among emerging adults; children's and adolescents' experience of loneliness and social dissatisfaction in the context of social, economic and cultural changes, and a review on the existing literature on the antecedents of psychological loneliness with special emphasis on emotional factors. It is widely acknowledged that individuals with autism spectrum disorders spend a lot of time in isolation, since they have difficulties interacting with peers or significant others. The most prevalence and promising interventions for overcoming loneliness in these individuals is critically evaluated in this book and suggestions for improvements and further research are made. The authors of other chapters also discuss the role of loneliness in the dynamic that leads some victimized adolescents to attack their peers; the need for effective treatments targeting loneliness; the relationship between dying and loneliness; the psychological effects of loneliness in immigrants parents and their relationship to anger; and finally, the factors that may predict the level of loneliness among immigrants (including self-esteem, contact with national peers, gender and duration of residence).