Amendment 01 approved by the Ethics Committee of the University of Cologne: The ethics committee of the University of Cologne made the following conditions for the initial approval of the trial protocol: 1. Addition to the exclusion criteria: intended pregnancy during the study. 2. Cardiovascular diseases should be included in the exclusion criteria, as hypersensitivity to aripiprazole administration must be expected. 3. Exclusion criteria should be expanded to: The person concerned has not been committed to an institution by virtue of an order issued by judicial or administrative authorities. 4. The wording concerning the termination of the study in the case of suicide or SAEs should be clarified (e.g. by stating rates) or deleted, as this is already included under "safety reasons". 5. Correct that during the visits, not only adverse Reactions but also adverse events are documented. 6. Even if allergic reactions to placebo cannot be ruled out, they should not be considered "expected" but treated as SUSAR if necessary. 7. We assume that by and large patients will be in the normal range of laboratory parameters. Therefore, any change of these parameters outside of the norm or changes in vital signs, (ECG), and changes that are otherwise considered clinically relevant by the investigator should be documented as an adverse event. 8. On page 112, 'initials' should be deleted, since according to Section 4.6.6 a patient ID is assigned without initials, and the use of initials must be considered inadmissible under data protection law.

Amendment 02, Protocol version 6.1 approved by the Ethics Committee of the University of Cologne: Based on the experience gathered since the start of the PREVENT trial, the following changes were necessary to improve the feasibility of the study and increase its practicability. There was no change in the primary endpoints; the secondary endpoints were expanded. 1. Physical examinations (ECG and laboratory parameters) were reduced to improved feasibility. 2. Specifications of how blood samples are to be taken, processed and stored were added. 3. Inclusion of the additional secondary endpoint "neurotrophic factors and oxidative stress as an add on to the study.

Amendment 03 Protocol version 8.0 approved by the Ethics Committee of the University of Cologne: 1. Four additional centres were added to speed up recruitment. 2. Change of principal investigator in Düsseldorf was documented. 3. Inclusion criteria were revised from 40 to 49 years to accelerate recruitment. 4. Exclusion criteria were made more specific for better comprehensibility or were narrowed down in some points in order to include a larger group of patients (exclusion criterium: "current or past antipsychotic treatment for longer than 1 week: current or past antipsychotic treatment shorter than 1 week without a washout phase of at least 4 weeks "was changed to: "current or past antipsychotic treatment without a washout phase of at least 4 weeks. " 5. As the trial fell short of its recruitment goals, the time schedule was extended. 6. Contact details of principal investigators were updated. 7. Due to delays in the inclusion diagnostics, imaging (MRT) should be alternatively performed by CT. 8. The assessment frequency of the "Social Adjustment Scale" was reduced, since the scale refers to the period of the last three months on the one hand, and the survey dates were assessed as sufficient by the study director on the other.

Amendment 04 Protocol version 3.0 approved by the Ethics Committee of the University of Cologne: 1. The trial did not meet its recruitment milestones. Thus, the power calculation was revised. The number of subjects to be included was reduced from 380 to 300. 2. Declining event rates were reported by studies in the field. Thus the primary endpoint "transition to psychosis" was expanded to "progression to psychosis". 3. In order to improve recruitment, two recruiting centres were added to the study. 4. Contact details were updated.