Think: Loneliness and Isolation
"...the whole existential approach is rooted in the always curious phenomenon that we have in man a being who not only can but must, if he is to realize himself, question his own being."
The Discovery of Being -- Writings in Existential Psychology -- by Rollo May is a superior introduction to Existential Psychology. If one is concerned with the causes of loneliness and isolation, in the human being -- which is also a major theme of the Existentialist school of thought -- this book is an excellent place to start. The Discovery of Being is a brisk, unclouded read. Stimulating would be an understatement, to say the least.
For those interested in how Existential Psychology applies to Existentialism and Phenomenology, there is a section dealing with Kierkegaard, Nietzsche and Freud...as background material. Other interest peaking sections that I enjoyed: How Existentialism and Psychoanalysis Arose out of the Same Cultural Situation, To Be and Not to Be, Anxiety and Guilt as Ontological, Being in the World, and The Three Modes of World. That should be enough to whet one's appetite. --Katharena Eiermann, 2005, the Realm of Existentialism -- Presidential Hopeful