Complex trajectories of ansiety across adolescence. Towards the discovery of new markers for early detection and treatment

Resumen

Anxiety constitutes an actual health hazard for contemporary societies with a dramatic impact on economy and daily life. Current diagnostic manuals take a look at anxiety just considering the full-blown anxiety disorders (ADs). Unfortunately, individuals who do not fully match all the AD criteria, but suffer significantly from anxiety symptomatology, have systematically been overlooked for mental health care. For that reason, a more flexible, non-categorical approach to deal with psychopathology is needed to be followed. The Research Domain of Criteria (RDoC) initiative proposes a multidimensional (neither static nor categorical) standpoint for anxiety to be studied. Thus, varying sources of distress, either clinical or subclinical, would be considered from this framework. This is especially relevant in the study of adolescent anxiety. Anxiety in adolescence is proved to be a strong predictor of different mental disorders in adulthood (e.g., depression, substance abuse disorders, etc.), even when anxiety symptomatology does not reach the level of clinical meaningfulness. Therefore, it turns into crucial to identify sensitive markers of adolescent anxiety which guide clinical assessment and intervention. In this regard, recent lines of research have highlighted how valuable are the measures derived from the Dynamical Systems Theory (DST) in featuring human socioemotional and physiological systems of individuals with psychological problems (identifying biomarkers, clarifying mechanisms of action, etc.). The main goal of this doctoral dissertation was to shed light on the search for accurate markers of anxiety in adolescence, allowing mapping individuals experiencing varying conditions onto the continuum of anxiety. To satisfy this aim, a meta-analytic study of scientific literature review (Study 1) and three empirical studies were conducted. The first empirical study (Study 2 within the thesis) covered the subjective research domain (by means of self-reports), and the two others (Study 3 and 4) were focused on identifying markers in the physiological research domain (in the cardiac system, concretely). As a secondary aim, it was intended to provide and test a prevention program to ameliorate the symptomatology of individuals suffering an anxiety-related condition. This aim was satisfied by performing a study (Study 5) to test the efficacy of an evidence-based preventive program for ameliorating internalizing symptomatology in adolescence. To summarize the relevant findings from the five studies mentioned, some relevant measures (e.g., sample entropy or fractal dimension in the cardiac, brain and hormonal systems) turned out to be sensitive for ADs were found from the Study 1. Regarding the Study 2, a depiction of the trajectory of anxiety symptomatology from early to middle adolescence was provided, highlighting the dynamical influence of some risk factors (temperament and gender) on its developmental course. The Study 3 and 4 enabled the identification of some cardiac biomarkers in adolescents with several conditions of subclinical anxiety: the allometric exponent h was proved to be an accurate biomarker in ecological contexts (Study 3); moreover, the sample entropy index turned out to be valuable when adolescents underwent a laboratory-based stress-induction task (Study 4). Finally, the Study 5 demonstrated that the preventive program delivered cut out efficiently the rising trajectory of anxiety observed in some adolescents as a risk factor for full-blown ADs. To sum up, some relevant markers (subjective and cardiac-derived) were identified from the studies conducted within this doctoral dissertation to map individuals onto the anxiety continuum. These markers were found as a result of following a flexible, developmental and psychopathological perspective in the study of anxiety in adolescence. Relevant implications for clinical assessment and intervention are derived from this doctoral dissertation in favor of planning tailored-based protocols and the promotion of prevention policies in order to facilitate healthier socioemotional maturation in adolescence.