Effectiveness of App-based Relaxation for Patients With Chronic Low Back Pain (Relaxback)

Inclusion Criteria: * female or male * 18-65 years of age * chronic low back pain for at least 12 weeks * if additional back pain is reported, low back pain has to be predominant * intensity of the average low back pain ≥ 4 on the numeric rating scale (NRS) in the last week * presence of a smartphone (iphone, Android phone) and willingness to do data entry through a smart phone application (App) * willingness to be randomized, to apply study intervention according to the protocol, to complete the baseline questionnaire in paper form and electronic questionnaires and diaries provided by an App physical and mental ability to participate in the study * written and oral informed consent Exclusion Criteria: * low back pain caused by a known malignant disease * neck pain caused by trauma * known rheumatic disorder * history or planned surgery of the spinal column of the low back in the next 6 months * known neurological symptoms e.g radicular symptoms because of prolapsed vertebral disc * regular intake of analgesics (\>1x per week) because of additional diseases * intake of centrally acting analgesics * known severe acute or chronic disorder, that do not allow participation in the therapy * other known diseases, that do not allow participation in the therapy * known alcohol or substance abuse * no sufficient German language skills * current application for a benefit * participation in another clinical trial during six months before the study and parallel to the study * conducting regular relaxation techniques, mindfulness training or meditation six weeks before the study or planned in the next 6 months