Table 1.

Study characteristics of included studies.

Author, year; rheumatic condition; percentage female	Intervention and control group, n	Dropout, na (%)	Country	Intervention duration; mode, frequency, and duration of therapist contact	Type of therapist	Follow-up period
Shigaki et al., 2013 Rheumatoid arthritis Percentage female: 92%	Internet-based cognitive-behavioral therapy, 55 Waiting list, 53	Intervention 11 (20%) Measurement 15 (14%) Intervention follow-up 12 (22%) Measurement follow-up 20 (19%)	USA	Intervention duration: 10 weeks Mode/frequency/duration therapist contact: weekly telephone contact, ca. 15-30 min. Contact between patients was possible via biweekly scheduled chats, a discussion board, and a secured messaging system.	Counselor with master's degree, trained in cognitive-behavioral therapy.	9 months after treatment
Friesen et al., 2017 Fibromyalgia Percentage female: 95%	Internet-based cognitive-behavioral therapy, 30 Waiting list, 30	Intervention 5 (17%) Measurement 8 (14%) Intervention follow-up 13 (44%) Measurement follow-up 16 (27%)	Canada	Intervention duration: 8 weeks Mode/frequency/duration therapist contact: contact via telephone or secured messaging. Weekly 5-10 min telephone contact.	Doctorate-level graduate student in clinical psychology.	No follow-up for the waiting list condition; 1 month follow-up after treatment for the internet-based cognitive-behavioral therapy condition.
Lorig et al., 2008 Rheumatoid arthritis 28%; osteoarthritis 64%; fibromyalgia 52%; other arthritic conditions 14% Percentage female (total sample): 90%	Internet-based cognitive-behavioral therapy, 433 Care-as-usual, 422	Intervention 123 (29%) Measurement 214 (25%) Intervention follow-up 126 (29%) Measurement follow-up 204 (24%)	USA	Intervention duration: 6 weeks Mode/frequency/duration therapist contact: online bulletin board and e-mail reminders; frequency and duration of contact unclear.	Peer moderators.	12 months after entry to treatment
Ferwerda et al., 2017 Rheumatoid arthritis Percentage female: 64%	Internet-based cognitive-behavioral therapy (care-as-usual + tailored internet-based cognitive-behavioral therapy), 62 Care-as-usual, 71	Intervention 17 (28%) Measurement 32 (24%) Intervention follow-up 33 (54%) Measurement follow-up 64 (49%)	The Netherlands	Intervention duration: 9–65 weeks (M = 26.07, SD = 12.22) 25% completed intervention in 17 weeks, 75% completed it in 32 weeks Mode/frequency/duration therapist contact: weekly or biweekly email contact.	Psychologists with master's degree, under supervision of senior psychologist.	3, 6, 9, 12 months after treatment
Vallejo et al., 2015 Fibromyalgia Percentage female: 100%	Internet-based cognitive-behavioral therapy, 20 Cognitive-behavioral therapy, 20 Waiting list, 20	Intervention 0 (0%) Measurement 0 (0%) Intervention follow-up 3 (15%) Measurement follow-up 7 (12%)	Spain	Intervention duration: 10 weeks Mode/frequency/duration therapist contact: internet-based cognitive-behavioral therapy: contact via online messaging. Frequency and duration of contact unclear. Cognitive-behavioral therapy: face-to-face group contact: 10 weekly sessions, each lasting 120 min.	Internet-based cognitive-behavioral therapy: junior therapist under supervision of senior therapist. Cognitive-behavioral therapy: doctoral-level therapist.	No follow-up for the waiting list condition; 3 follow-up assessments at 3, 6, and 12 months after treatment for the internet-based cognitive-behavioral therapy and cognitive-behavioral therapy conditions.
Peters et al., 2017 Fibromyalgia 67%; other musculoskeletal pain 33% Percentage female (total sample): 85%	Internet-based cognitive-behavioral therapy, 116 Positive Psychology intervention (PPI), 117 Waiting list, 51	Intervention 36 (31%) Measurement 78 (28%) Intervention follow-up 61 (53%) Measurement follow-up 135 (48%)	The Netherlands/Belgium	Intervention duration: 9 weeks Mode/frequency/duration therapist contact: both ICBT and PPI: Telephone (weeks 1, 3, 5, and 7) and e-mail (weeks 2, 4, 6, and 8) support. Average duration of telephone contact was 15-20 min.	Both conditions: graduate or recently graduated psychologists.	No follow-up for the waiting list condition; 6 months follow-up after treatment for the Internet-based cognitive-behavioral therapy and positive psychology intervention.
Simister et al., 2018 Fibromyalgia Percentage female: 95%	Online acceptance and commitment therapy + care-as-usual, 33 Care-as-usual, 34	Intervention 6 (19%) Measurement 9 (14%) Intervention follow-up 8 (25%) Measurement follow-up 17 (26%)	Canada	Intervention duration: 2 months Mode/frequency/duration therapist contact: e-mail reminders on a weekly basis and feedback messages.	Registered psychologist.	3 months after treatment.
Hedman-Lagerlöf et al., 2018 Fibromyalgia Percentage female: 98%	Internet-delivered exposure therapy, 70 Waiting list, 70	Intervention 2 (3%) Measurement 2 (2%) Intervention follow-up 4 (6%) Measurement follow-up 4 (3%)	Sweden	Intervention duration: 10 weeks Mode/frequency/duration therapist contact: about 1 to 3 times/week coaching via asynchronous text messages. Reminders via text message or phone if a participant had been inactive for 4 days. In total, the average time therapists spent per participant was 2.9 h (SD = 2.1; median = 2.6; IQR = 2.6).	Licensed psychologists or graduate psychology students. Weekly supervision by a licensed psychologist with experience in treating fibromyalgia.	No follow-up for the waiting list condition, 3 months and 6 months follow-up after treatment for the internet-delivered exposure therapy.

^aSee materials and methods.