Internet-delivered treatment for patients suffering from severe functional somatic disorders: Protocol for a randomized controlled trial

•This is the first e-based treatment for severe functional somatic disorders.•Two active conditions, a guided and an unguided treatment program, are compared.•We expect both programs will prove effective in enhancing physical health.•We hypothesize that the guided program will be superior to the unguided in effect.•If effective, e-based treatment can make specialized treatment more accessible.