BACKGROUND: Internet-based interventions using cognitive behavioral approaches 
can be effective in promoting self-management of chronic pain conditions. 
Web-based programs delivered via smartphones are increasingly used to support 
the self-management of various health disorders, but research on smartphone 
interventions for persons with chronic pain is limited.
OBJECTIVE: The aim of this trial was to study the efficacy of a 4-week 
smartphone-delivered intervention with written diaries and therapist feedback 
following an inpatient chronic pain rehabilitation program.
METHODS: A total of 140 women with chronic widespread pain who participated in a 
4-week inpatient rehabilitation program were randomized into 2 groups: with or 
without a smartphone intervention after the rehabilitation. The smartphone 
intervention consisted of 1 face-to-face session and 4 weeks of written 
communication via a smartphone. Participants received 3 smartphone diary entries 
daily to support their awareness of and reflection on pain-related thoughts, 
feelings, and activities. The registered diaries were immediately available to a 
therapist who submitted personalized written feedback daily based on cognitive 
behavioral principles. Both groups were given access to a noninteractive website 
after discharge to promote constructive self-management. Outcomes were measured 
with self-reported questionnaires. The primary outcome measure of 
catastrophizing was determined using the pain catastrophizing scale (score range 
0-52). Secondary outcomes included acceptance of pain, emotional distress, 
functioning, and symptom levels.
RESULTS: Of the 140 participants, 112 completed the study: 48 in the 
intervention group and 64 in the control group. Immediately after the 
intervention period, the intervention group reported less catastrophizing (mean 
9.20, SD 5.85) than the control group (mean 15.71, SD 9.11, P<.001), yielding a 
large effect size (Cohen's d=0.87) for study completers. At 5-month follow-up, 
the between-group effect sizes remained moderate for catastrophizing (Cohen's 
d=0.74, P=.003), acceptance of pain (Cohen's d=0.54, P=.02), and functioning and 
symptom levels (Cohen's d=0.75, P=.001).
CONCLUSIONS: The results suggest that a smartphone-delivered intervention with 
diaries and personalized feedback can reduce catastrophizing and prevent 
increases in functional impairment and symptom levels in women with chronic 
widespread pain following inpatient rehabilitation.
TRIAL REGISTRATION: Clinicaltrials.gov NCT01236209; 
http://www.clinicaltrials.gov/ct2/show/NCT01236209 (Archived by WebCite at 
http://www.webcitation.org/6DUejLpPY).