Key PointsQuestion
Which specific components within internet-delivered cognitive
behavioral therapy (CBT) for depression are active ingredients that
reduce symptoms?
Findings
In this randomized optimization trial that included 767 adults
with depression, 6 treatment components (activity scheduling, thought
challenging, relaxation, concreteness training, functional analysis, and
self-compassion training) did not show a significant main effect on
depression. However, the presence of the absorption component
outperformed its absence in reducing depression at 6-month follow-up.
Meaning
The findings suggest that the majority of treatment benefit
from internet-delivered CBT is likely to accrue from factors common to
all CBT components and/or from generic factors common to all therapies,
with the possible exception of absorption.
Importance
There is limited understanding of how complex evidence-based
psychological interventions such as cognitive behavioral therapy (CBT)
for depression work. Identifying active ingredients may help to make
therapy more potent, brief, and scalable.
Objective
To test the individual main effects and interactions of 7
treatment components within internet-delivered CBT for depression to
investigate its active ingredients.
Design, Setting, and Participants
This randomized optimization trial using a 32-condition,
balanced, fractional factorial optimization experiment (IMPROVE-2)
recruited adults with depression (Patient Health Questionnaire−9 [PHQ-9]
score ≥10) from internet advertising and the UK National Health Service
Improving Access to Psychological Therapies service. Participants were
randomized from July 7, 2015, to March 29, 2017, with follow-up for 6
months after treatment until December 29, 2017. Data were analyzed from
July 2018 to April 2023.
Interventions
Participants were randomized with equal probability to 7
experimental factors within the internet CBT platform, each reflecting
the presence vs absence of specific treatment components (activity
scheduling, functional analysis, thought challenging, relaxation,
concreteness training, absorption, and self-compassion training).
Main Outcomes and Measures
The primary outcome was depression symptoms (PHQ-9 score).
Secondary outcomes include anxiety symptoms and work, home, and social
functioning.
Results
Among 767 participants (mean age [SD] age, 38.5 [11.62] years;
range, 18-76 years; 635 women [82.8%]), 506 (66%) completed the 6-month
posttreatment follow-up. On average, participants receiving
internet-delivered CBT had reduced depression (pre-to-posttreatment
difference in PHQ-9 score, −7.79 [90% CI, −8.21 to −7.37]; 6-month
follow-up difference in PHQ-9 score, −8.63 [90% CI, −9.04 to −8.22]). A
baseline score–adjusted analysis of covariance model using effect-coded
intervention variables (−1 or +1) found no main effect on depression
symptoms for the presence vs absence of activity scheduling, functional
analysis, thought challenging, relaxation, concreteness training, or
self-compassion training (posttreatment: largest difference in PHQ-9
score [functional analysis], −0.09 [90% CI, −0.56 to 0.39]; 6-month
follow-up: largest difference in PHQ-9 score [relaxation], −0.18 [90%
CI, −0.61 to 0.25]). Only absorption training had a significant main
effect on depressive symptoms at 6-month follow-up (posttreatment
difference in PHQ-9 score, 0.21 [90% CI, −0.27 to 0.68]; 6-month
follow-up difference in PHQ-9 score, −0.54, [90% CI, −0.97 to −0.11]).
Conclusions and Relevance
In this randomized optimization trial, all components of
internet-delivered CBT except absorption training did not significantly
reduce depression symptoms relative to their absence despite an overall
average reduction in symptoms. The findings suggest that treatment
benefit from internet-delivered CBT probably accrues from spontaneous
remission, factors common to all CBT components (eg, structure, making
active plans), and nonspecific therapy factors (eg, positive
expectancy), with the possible exception of absorption focused on
enhancing direct contact with positive reinforcers.
Trial Registration
isrctn.org Identifier: ISRCTN24117387