Living up to expectations? A simulation study evaluating methods used to detect sudden gains and sudden losses.

Sudden gains and sudden losses are abrupt, large changes in symptom severity between two consecutive psychotherapy sessions. Sudden gains (i.e., large improvements in symptom severity) seem to be associated with better treatment outcomes and have thus received considerable attention in clinical psychology over the last 2 decades. However, simulation studies indicate that the most common approach used to detect sudden gains is prone to misclassifications, implying that sudden gain research might be hindered by false positive and false negative findings. Although other sudden gain detection approaches exist, their performance has not yet been investigated and compared to the conventional method. To close this gap, we conducted a simulation study comparing the performance of the conventional approach and four alternative sudden gain detection approaches depending on the type of symptom trajectory, the number of measurements, the reliability of the measurement scores, and the amount of fluctuation around the trajectories. We found that all five detection approaches performed well in the simulation condition with nearly no variability (i.e., low reliability and small fluctuations). However, in conditions with medium or high variability in the data, all detection methods performed poorly. These results suggest that future studies should investigate further potential methods to detect sudden gains and/or examine ways to improve existing methods, such as by considering measurement error. (PsycInfo Database Record (c) 2024 APA, all rights reserved).