Table 1 Inclusion and exclusion criteria

1) ≥ 18 years.

2) Able to speak, read, and write Dutch.

3) Able to use a computer and have access to Internet.

4) CFS diagnosis according to the CDC consensus criteria:

[1, 2]

5) Severe fatigue is assessed with the subscale fatigue severity of the Checklist Individual Strength (CIS). Severe fatigue is operationalized as scoring ≥ 35.

[23]

6) Disabilities; Disability is assessed with the total score of the Sickness Impact Profile (SIP8). Severe disability is operationalized as a total score ≥ 700 on the SIP8.

[27, 41]

7) Given written informed consent.

Exclusion criteria

1) Engaged in a legal procedure concerning disability-related financial benefits.

2) Participating in other CFS research.