The timing and magnitude of symptom improvements during an Internet-delivered transdiagnostic treatment program for anxiety and depression.

Objective: In face-to-face treatments, mental health symptoms improve rapidly across the first few treatment sessions, and the pace of improvement slows with additional sessions. Some individuals also report clinically meaningful symptom improvements after only two or three treatment sessions. As the rate of symptom change has been given limited attention within digital treatments, the present study investigated the timing and magnitude of symptom change during an 8-week online treatment for anxiety and depression.

Method: Three adult samples were derived from previous randomized controlled trials: generalized anxiety disorder ( = 165), major depression ( = 149), and mixed anxiety/depression ( = 262). Symptom scores were compared between consecutive weeks of treatment, and we examined the proportion of individuals who achieved a ≥ 25% or ≥ 50% improvement in symptoms each week.

Results: Across all three samples, symptoms improved more rapidly during the first half of treatment compared to the second half of treatment. Within the first 4 weeks, over half of the participants had experienced a ≥ 25% improvement in symptoms, and approximately a third of participants had experienced a ≥ 50% improvement in symptoms. This pattern of change was found irrespective of diagnostic status or outcome measure.

Conclusions: A substantial number of people who receive internet-delivered treatments appear to experience rapid, large, and clinically significant symptom improvement early in treatment. These findings add to our theoretical understanding of symptom improvements during psychotherapy, and further research investigating the mechanisms of such change will inform the development of more effective treatments. (PsycInfo Database Record (c) 2023 APA, all rights reserved).