Randomized, controlled, double-blind, two-armed clinical investigation to show the efficacy and safety of transcutaneous vagus nerve stimulation (t-VNS), applied at the left auricle, in schizophrenia.

Study hypothesis: t-VNS may improve negative symptoms, depressive symptoms, cognitive impairment,and aggressive behavior of treated schizophrenia patients.

Inclusion Criteria:

• Diagnosis of a schizophrenic disorder (F20 according to ICD-10),duration of disease ≥ 12 months
• Appliance of the t-VNS® medical device according to the manual

Exclusion Criteria:

• Improvent of the PANSS score within the period of 2 - 4 weeks from screening to the baseline
• Pregnancy
• Bronchial asthhma in medical history
• clinically relevant internistic, neurological or psychiatric diseases
• abuse of drugs or alcohol until 4 weeks to enrollment
• Traumatic brain injury in medical history as well as invasive and non-invasive methods of treatment (e.g. tumor surgery (Gammma knife surgery))
• indication of structural impairment of the basal ganglia or the brain stem
• malformations of the pinna
• further circumstances that at the discretion of the investigator will not allow to include the subject into the clinical study