[ca] La depressió és un dels trastorns més prevalents i una de les principals causes de discapacitat a nivell mundial. Pel que fa a les seves implicacions econòmiques, els trastorns depressius també tenen un important impacte en els pressupostos sanitaris a través tant de costos directes com indirectes. Estudis previs sobre el seu curs clínic han mostrat que sovint aquests trastorns es cronifiquen, fenomen relacionat amb la seva elevada recurrència. A més a més, és comú trobar altres trastorns que es presenten de forma conjunta amb la depressió. Una malaltia física altament prevalent entre les persones amb depressió és la fibromiàlgia, comorbiditat que ja ha demostrat tenir un impacte significatiu en el funcionament i el benestar. L'objectiu principal d'aquesta tesi era el d'avançar el coneixement sobre la relació entre la depressió i la felicitat autoinformada, així com comprovar si la psicoteràpia era capaç d'augmentar la felicitat de les persones amb depressió. Per assolir aquests objectius, vam dur a terme dos estudis interrelacionats. El primer (transversal) va mesurar la relació entre depressió i felicitat a través de comparar una mostra no clínica, una mostra de pacients amb depressió, i una altra de pacients amb depressió i fibromiàlgia. El segon estudi (assaig controlat aleatoritzat) va analitzar com la felicitat evolucionava amb la psicoteràpia, comparant dues modalitats. Els resultats van mostrar que els participants amb depressió eren significativament menys feliços que els de la mostra no clínica, mentre que patir fibromiàlgia comòrbida a la depressió no produïa un efecte perjudicial addicional. Després de la psicoteràpia, es van trobar grans augments en la felicitat de les persones amb depressió, independentment del seu gènere, edat, estat civil, nivell educatiu, situació laboral, ús actual de medicació psicotròpica, i modalitat de tractament rebuda. Aquesta tesi constitueix, pel que sabem, el primer estudi que analitza la felicitat en trastorns depressius des d'una perspectiva constructivista, la qual para especial atenció a la identitat i els significats personals de les persones. En general, els resultats presenten la felicitat com un focus de teràpia important i útil que pot ser incorporat al tractament de la depressió.

[en] Depression is one of the most prevalent disorders and one of the leading causes of disability worldwide. Regarding economic implications, depressive disorders have also a large impact on health budgets through both direct and indirect costs. Studies on their clinical course have shown that they often become chronic, a phenomenon related to their high recurrence rates. In addition, it is usual to find other disorders co-occurring with depression. Such comorbidities not only increase its severity, but also decrease response to treatment, and produce further impairment in individuals' life. A physical disease highly prevalent among people with depressive disorders is fibromyalgia syndrome, a comorbidity that has already been shown to produce a significant impact in daily functioning and wellbeing, and to decrease response to treatment. The main objective of this thesis was to advance the knowledge on the relationship between depression and self-reported happiness, analysing how several clinical conditions, and the cognitive system involved in the construction of self and others, influenced such relationship. Furthermore, we also tested whether psychotherapy was capable of increasing happiness in individuals with depression. To pursue these objectives, two interrelated studies were conducted. The first study (cross-sectional) gauged the relationship between depression and happiness by comparing a non-clinical sample with 81 participants, a sample of 91 patients with depression, and a sample of 61 with depression plus fibromyalgia syndrome. In the second study (a randomised controlled trial), we analysed how happiness evolved with psychotherapy, comparing two different therapeutic approaches (cognitive-behavioural therapy, and dilemma- focused therapy) delivered to 97 participants. Results showed that participants with depression were significantly less happy than those in the non-clinical sample, whereas suffering fibromyalgia syndrome comorbid to depression did not have a further detrimental effect. After psychotherapy, large increases in happiness were found among people with depression, regardless their gender, age, civil status, education, labour status, current use of psychotropic medication, and the treatment modality they received. Experiencing cognitive conflicts had a slightly detrimental influence on happiness which, in addition, was negatively correlated with depression severity and psychological distress, and positively with global functioning. Negative self-evaluation and perceived self-isolation showed also a significant association with happiness among participants with depression, whereas having a negative view of others was relevant only for individuals suffering both depression and fibromyalgia syndrome. In turn, only among participants in the non- clinical group, higher levels of happiness were associated with more polarised and unidimensional thinking, and a weak relationship was also observed between the level of happiness attributed to their parents and their own. In general, participants construed being happy as similar to being cheerful, good, and hard-working, and at the same time very different to being sad, bad, and embittered. We also observed a tendency in all participants to construe disliked persons as not happy, while individuals with depression construed themselves similarly as not happy. Finally, increases in happiness with therapy were associated with higher resolution of cognitive conflicts, with more unidimensional thinking, and with improvements in depression severity, psychological distress, global functioning, negative self-evaluation, and perceived self-isolation. To our knowledge, this thesis constitutes the first study analysing happiness in depressive disorders from a constructivist perspective, which pays especial attention to individuals' identity and personal meanings. In addition, our results contribute to estimate the effect of psychotherapy for depression in happiness, for which previous data was scarce. Overall, with this thesis we provide evidence for the role of several clinical and cognitive indicators in the experience of happiness, such as psychological distress or interpersonal construct differentiation, and highlight happiness as a relevant focus of work that may be incorporated to the treatment of depression.