Sudden gains are large reductions in symptoms measured in a single between-session interval and are positively associated with long-term treatment outcomes. To date, sudden gains have mostly been observed in therapist-directed psychotherapies. There are currently mixed findings surrounding the mechanisms underlying sudden gains, with some support for a cognitive mechanism and some support for therapist characteristics such as the therapeutic alliance. In this study of 77 female survivors of childhood sexual abuse, sudden gains in trauma symptoms were found in a randomized clinical trial of a patient-directed expressive writing intervention. Women in the active treatment condition (who wrote about their beliefs related to sexuality or trauma) exhibiting sudden gains in trauma symptoms showed larger improvements in depression than those in the control condition (who merely wrote about their daily needs). The extension of sudden gains from psychotherapy to a client-directed treatment refines our understanding of the mechanisms underlying these gains, and supports the hypothesis that cognitive change is a likely mechanism underlying sudden gains.
