Trajectories of anxiety symptoms in adolescents: Testing the model of emotional inertia.

Two predictions derived from a recently introduced model of psychotherapy outcome were tested, assuming the dynamical relationship between the individual's emotional trajectory and the force of intervention necessary to change this trajectory: (a) only a high intensity treatment would succeed to lower the increasing trajectory of anxiety, and (b) high as well as low intensity treatments would equivalently lower the non-increasing trajectory of anxiety. : Seventy-four adolescents (58.40% girls; = 14.65 years, = 0.53) were randomly assigned to a high intensity treatment condition, a low intensity treatment condition, or a waiting list condition. Only the high intensity treatment reduced the anxiety when participants showed an increasing trajectory (< .01). None of the treatments reduced anxiety when a previously non-increasing trajectory was shown. These findings support the theoretical predictions and underscore the need to consider not only how severe the anxiety is but also the time course of anxiety in applied treatment settings.