Schizophrenia is a severe mental disorder which is accompanied by an enormous individual and societal burden. Despite established efficacy of cognitive behavioral therapy for psychosis (CBTp), its dissemination into routine mental health care remains poor. National regulations such as the National Institute for Health and Care Excellence (NICE) guideline in the United Kingdom recommend that CBTp should be offered to every person with psychotic symptoms, but more than 50% do not receive even a single session of CBTp. In Germany, CBTp is virtually not represented in the psychotherapy health service. Internet-based cognitive behavioral therapy (CBT) in a self-help format has been proven feasible and effective in anxiety and depressive disorders. Recently, Internet-based (self-help) interventions are also deployed via smartphone apps. The feasibility of Internet-based treatments for people with schizophrenia is well documented for Internet-based interventions (e.g., medication management) and also reported for smartphone interventions. However, there is a dearth of empirical studies precluding a conclusive picture. As far as the investigators know, there is only one study encompassing 90 participants with psychosis that investigated an Internet-based intervention with symptom-specific, cognitive behavioral interventions, which is from the investigators' research group. The unique features of the proposed project are 1) the first-time evaluation of a symptom-oriented, CBTp-based self-help treatment for people with psychotic symptoms via Internet, enhanced with smartphone assistance. The study is set up as randomized controlled trial (RCT) with active treatment versus a wait-list control group. It evaluates a combined Internet-based guided self-help treatment for persecutory ideation and auditory verbal hallucinations. The active treatment condition consists of access to a self-help website including regular written electronic contact with a guide and access to smartphone-based interactive worksheets (apps). The trials combine the low-threshold advantages of an online approach (e.g., anonymity) with the virtues of a clinical trial (e.g., symptom assessment and diagnostic verification via Interview). The primary outcome measure is the Positive and Negative Syndrome Scale (PANSS). Secondary outcome measures include self-reported symptom measures (Paranoia Checklist; Beliefs About Voices Questionnaire revised), completion rates, drop-out from the intervention, general symptomatology, side-effects, and client satisfaction. The project will help to answer the empirical question whether CBTp-based interventions in a purely Internet-based self-help format are effective. Positive findings would pave the way for an easy-to-access treatment option for patients with psychotic symptoms who currently are deprived of psychotherapeutic treatment.

Inclusion Criteria:

• Electronic informed consent
• Internet access
• Adequate command of the German language
• PANSS Suspiciousness/persecution >= 3 AND/OR PANSS hallucinations >=3
• Diagnosis of schizophrenia, schizoaffective disorder or delusional disorder
• Concurrent psychopharmacological treatment

Exclusion Criteria:

• Acute suicidality
• Acute risk of endangering others
• No emergency plan (with is formulated during the telephone interview)
• Disease of the central nervous system with need for treatment