The conceptual framework for my current research is the Nonlinear Dynamical Systems Theory. Adolescent anxiety is the psychological focus of my research. Specifically we investigate (a) the trajectories of the anxious symptomatology along the early adolescence (11 to 14 years-old students), (b) the relationships between these trajectories and some temperamental traits (e.g. sensitivity to punishment), (c) the dynamical characteristics of the cardiac signals from adolsecents with high versus low anxiety, and (d) the fluctuations in mood, anxiety, and emotion regulation strategies along time windows of different length (up to 100 days). This research is currently funded by the project PSI2012-34780 from the Spanish National R+D+i Plan.