Inclusion Criteria:  Age 18 or older Initial MADRS-Score of 22 or above Diagnosis of a therapy-resistant depression following the definition of the European Medicines Agency (EMA) - absence of remission after two or more guideline-oriented therapies Patients assigned to treatment with nasal esketamine spray Spravato® Signed informed consent Native German speaker Basic knowledge in using computers/smartphones operationalized as daily use of at least two devices (such as tablets, computers, smartphones etc)  Exclusion Criteria:  Contraindication regarding the use of Spravato® Diagnosis of one of the following psychiatric comorbidities: substance abuse, schizoaffective disorders, schizophrenia, bipolar disorder, organic disorders diagnosed via Mini International Neuropsychiatric Interview (MINI)