Effectiveness of Acceptance Commitment Therapy or Micro Breaks in Patients with Chronic Fatigue Syndrome/ Myalgic Encephalomyelitis

Inclusion Criteria: * Diagnosis for CFS/ME * Psychiatric clinical stability in the past 3 months: * No diagnostic change to other categories of the International Classification of Diseases (ICD-10) * No psychiatric inpatient treatments * No psychiatric emergency treatments * No suicide attempts * Possession of internet access * Sufficient skills to use electronic devices * The willingness to engage in the described therapeutic procedures or interventions (ACT, MBEL) Exclusion Criteria: * Insufficient knowledge of German * Severe psychiatric disorders (e.g. personality and posttraumatic stress disorders, dissociative and psychotic disorders, intelligence reduction, untreated attention deficit hyperactivity disorder) and acute suicidal tendencies * Untreated or severe internal medicine disorders e.g., thyroid dysfunction, central and obstructive sleep apnea syndrome (i.e., apnea-hypopnea index \>15 and/or "high-risk group for obstructive sleep apnea" according to the Berlin Questionnaire) * Cardiovascular disease such as chronic heart failure * Severe or untreated neurological diseases (e.g. Parkinson's disease, dementia, restless legs syndrome, narcolepsy) * Alcohol and drug dependence * Initiation of psychopharmacotherapy at a dosage provided for guideline-appropriate treatment of a mental disorder according to the Drug Compendium in the past 3 months * Start of other psychotherapy procedures in the last 3 months * Other parallel therapy methods (e.g. acupuncture, qigong, osteopathy) * Somatic (sleep-disrupting) treatments, cortisone treatment, or radio-/chemotherapy in the last 6 months