This loneliness won't leave me alone Emotional- and social loneliness in relation to social isolation, mental health, and cognitive processes in emerging adulthood

Young adults are impacted by loneliness just as much as older adults, if not more. Feeling lonely is a perceived negative emotional state and is relative to someone’s own relationships, experiences, and expectations. Loneliness is a complex construct with two dimensions, namely emotional- and social loneliness. Despite the fact that loneliness increases the risk for poor (mental) health and interpersonal functioning, only a few high quality treatment studies have been conducted and treatments aiming to alleviate loneliness are only moderately successful. Therefore, the goal of this dissertation was to gain more knowledge on the underlying mechanisms of emotional loneliness and social loneliness and their relation to psychosocial functioning, in order to identify more effective treatment targets. This dissertation showed support for the bidimensional nature of loneliness and how treatment effects might differ for emotional- and social loneliness. Furthermore, loneliness was associated with a content-specific negative interpretation bias related to the unavailability of the social network. Therefore, lonely young adults may be helped by the development of evidence-based CBT programs targeting the specific underlying negative interpretation bias associated with loneliness. In addition, internet-delivered CBT programs might be a useful tool to alleviate feelings of loneliness, but only if loneliness is targeted directly. Research is needed on the underlying cognitive mechanisms causing and maintaining emotional- and social loneliness to guide researchers in developing treatment programs targeting content-specific biases underlying loneliness. Finally, determining treatment moderators to develop personalised treatment of loneliness might derive more successful outcomes as loneliness is a complex issue.