| A sizable portion of the population experiences subthreshold depressive symptoms, and these symptoms can lead to substantial functional impairment. However, there is little research on psychological interventions for depressive symptoms in nonclinical populations. In a series of three studies, I examine the efficacy of Positive Psychotherapy (PPT)---an intervention designed to decrease depressive symptoms in mild-moderately depressed individuals by increasing pleasure, engagement, and meaning---both in-person and over the web. I also explore the mechanism by which PPT decreases symptoms without ever targeting depression directly.;In Study 1, I piloted a 6-week group PPT intervention. Participants randomly assigned to receive group PPT experienced fewer depressive symptoms and greater life satisfaction than did no-intervention controls. Decreases in depressive symptoms were mediated by increases in life satisfaction, but only partially. In Study 2, I examined the effects of the techniques used in PPT when administered individually. I randomly assigned participants to complete one of the six PPT exercises or a placebo control exercise. When analyzed as one group, PPT exercises led to significant improvement in depressive symptoms while the Control exercise did not. Both PPT exercises and the Control exercise increased life satisfaction. However, the PPT exercises did not significantly differ from the Control exercise on either outcome. In Study 3, I piloted an online version of PPT. Compared to assessment-only controls, online PPT participants experienced significantly fewer depressive symptoms. However, there were no significant effects on life satisfaction, nor on another potential mediator: positive emotion. There was substantial variation in rates of compliance and continued use for each exercise; however, three months later, 91% of those who completed the follow-up assessment were still practicing at least one of the six exercises, with the average participant continuing to use between 2 and 3 exercises.;Despite limitations, which include high dropout rates and structural rigidities due to the automated design of online PPT, this series of studies provides an important first step in developing a low-cost, acceptable intervention for decreasing mild-moderate depressive symptoms in nonclinical populations. |
