While intervention effects in target outcomes have typically been tested based on change from baseline to post-intervention, such approaches typically ignore individual differences in change, including time taken to see improvement. The present study demonstrates how weekly patient-reported data may be used to augment traditional pre–post intervention evaluations in order to gain greater insights into treatment efficacy.
Two hundred and fifty-two adolescent boys and girls (M age = 13.6 years, SD = 0.6 years) from four secondary schools in Victoria, Australia, were assigned by school into control (n = 88) or intervention (n = 164) groups. The intervention group participated in a 6-week course designed to improve subjective wellbeing (SWB) by fostering resilience, coping skills, and self-esteem. In addition to baseline, post-intervention, and 3-month follow-up assessments of SWB, intervention group participants also completed weekly summarise of affective experiences for the duration of the intervention phase.
While standard pre–post data showed significant improvement in SWB for the intervention group relative to controls, weekly data showed individual differences in the trajectory of change during this intervention phase; low SWB individuals experienced initial worsening of symptoms followed by improvement in the second half of the intervention phase, whereas high SWB individuals experienced initial gains, followed by a plateau from Week 4 onwards.
Addition of weekly data provided greater insights into intervention effects by: (1) contradicting the notion that early responsiveness to treatment is predictive of level of improvement by post-intervention, and (2) providing data-based insights into ways to enhance the intervention.