The path to an eating disorder (ED) always leads through a borderland, which, in this thesis, is referred to as disordered eating (DE) (Neumark-Sztainer, Wall, Eisenberg,Story, & Hannan, 2006; Waaddegaard, Thoning, & Petersson, 2003). In this borderland, people tend to make unhealthy eating choices, such as greatly reducing their food intake, self-inducing vomiting, or engaging in binge eating, but not to the extent that they would receive an ED diagnosis. Nevertheless, DE can have a strong negative effect on psychological health. Approximately 15%–52% of all adolescents, depending on the gender and the study’s focus, are found within the borderland between a healthy diet accompanied by psychological well-being and full-blown ED (e.g. Hautala et al., 2011; Herpertz-Dahlmann et al., 2008). While most of these individuals return to a more or less healthy diet after engaging in DE for some time, others continue to engage in DE and also tend to have trouble regulating their emotions, depression, and low self-esteem. For these reasons, DE itself, apart from being a springboard to EDs, is well worth exploring.At the outset of this thesis, an instrument assessing DE among 1265 adolescents (54.5% girls) was validated. This easily administered questionnaire, referred to by the acronym SCOFF (Morgan, Reid, & Lacey, 1999), comprises five questions assessing possible eating disturbances that are all answered using a “yes”/“no” answer format. The results showed that more girls than boys suffered from DE, and that girls also suffered from more severe DE, which is in line with previous research (e.g. Hautala et al., 2008). Additionally, this assessment of the SCOFF gave rise to the question of whether a positive answer on only certain items (instead of the stipulated cut-off of two) is necessary for indicating the possible presence of DE among adolescents, such as the item assessing whether individuals had ever vomited because they felt uncomfortably full.To further explore DE among adolescents, a person-oriented approach to identify specific patterns of DE based on the subscales of the Eating Disorders Examination Questionnaire (EDE-Q) (restraint, eating, weight, and shape concerns) was used. There were six different DE patterns for both boys and girls. The associations of these patterns with emotion dysregulation, depressive symptoms, and self-esteem, which all are related to DE (e.g. Shea & Pritchard, 2007; Svaldi, Griepenstroh, Tuschen- Caffier, & Ehring, 2012), were also assessed. Four of the six girl clusters and five of the six boy clusters showed scores above the cut-off for a clinical ED on at least one of the four indicators. Furthermore, although the “non-problematic” pattern was substantial, including 50% and 76% of girls and boys, respectively, a large portion of adolescents were part of clusters reporting generally high levels of DE. This might partly have to do with my use of an overly permissive cut-off, but nevertheless indicates that a considerable amount of adolescents suffer from DE. Generally, individuals in the DE patterns showed worse emotion regulation, depressive thoughts, and self- esteem than did those in the “non-problematic” patterns. However, some exceptions were found, which emphasizes the utility of analyzing different patterns of DE, not merely severity. Specifically, both girls and boys belonging to the pattern characterized by scores well above the cut-off on shape and weight concerns reported the lowest levels of self-esteem. Moreover, girls and boys in the pattern with scores above the cut-off on restraint showed good emotion regulation skills, few depressive symptoms, and high self-esteem.In Study III, the possible links between adolescents’ and parents’ possible DE and emotion dysregulation were explored, alongside the possible impact of shared family meals on DE. This study further examined whether it is possible to predict DE among adolescents according to their parents’ behaviors. Both DE and emotion dysregulation were found to be more frequent among adolescents than among parents. Furthermore, both adolescents and parents showed weak but significant associations between DE and emotion dysregulation, and showed similarities regarding specific aspects of emotion regulation, although the associations were gender specific. For example, parental emotional strategies were associated with girls’ emotional strategies, impulse control, and emotional goals, but only with boys’ emotional strategies. The only factor that was (weakly) associated with DE and emotion regulation among adolescents was the number of dinners that they shared with the family. Additionally, parental ED was the only predictor of current adolescent DE.In summary, the results of this thesis showed that many adolescents, especially girls, suffer from DE as well as poor emotional regulation, depressive thoughts, and low self-esteem. This is a problem, especially given that existing instruments for evaluating DE do not seem optimal, especially for boys. For instance, answering “yes” to the question of ever having engaged in self-induced vomiting because you have felt too full is probably best followed by a visit to the school nurse. Furthermore, the results indicated the importance of viewing DE not as a singular problem, but as a collection of different problems, even among individuals of the same gender. These differences call for different strategies aimed at helping adolescents achieve a healthier diet. Finally, while the parental influence of DE was significant, more research is required,preferably in a Swedish or Nordic context, where parental responsibility is not as heavily reliant on the mother as in other countries.