Effect modifiers of internet-based stress-management. Results from three randomized trials

  • K. Weisel
  • D. Lehr
  • E. Heber
  • M. Berking
  • A. Zarski
  • D.D. Ebert


Background: Internet-based and mobile-supported stress management interventions (iSMIs) may be a promising strategy to reach impaired employees suffering from high chronic stress that would otherwise not make use of mental health interventions. However, it remains unknown whether severely impaired individuals, such as those with high levels of depression or anxiety, also profit from preventative iSMIs. The study aimed to identify moderators of treatment outcomes. Methods: Data from three RCTs (N=791), designed to test the effectiveness of iSMIs, were pooled to identify effect modifiers and evaluate effectiveness in subgroups with different levels of initial symptom severity. The outcomes perceived stress, depressive and anxiety symptom severity were assessed at baseline, 7-week posttreatment, and 6-month follow-up. In multiple moderation analyses potential moderators were tested in predicting differences in change of outcome. Through simple slope analyses effectiveness of the iSMI was compared in subgroups with low, moderate and severe initial symptomology. Findings: Highly stressed individuals profited more from the intervention through greater reduction of stress (low stress: d = .66, high stress: d = 1.27), depressive symptoms (low stress: d = .6, high stress: d = 1.14) and anxiety (moderate stress: .84, high stress: 1.14) after 6 months. Individuals with higher depression at baseline showed greater reduction of depressive symptoms (low depression d = .79, high depression d = 1.02) and greater anxiety predicted higher anxiety reduction (low anxiety: d = .76, high anxiety: d = 1.16). Discussion: Highly impaired individuals benefit greatly from iSMIs and should, therefore, not be excluded from participation.