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Study on Cannabidiol as an Add-On Treatment for Patients with Early Schizophrenia

Verified siteInvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the effects of a treatment for schizophrenia, specifically in its early stages. The treatment being tested is cannabidiol, which is a chemical compound found in cannabis plants. In this study, cannabidiol is being compared to a placebo, which is a substance with no active therapeutic effect. The purpose of the study is to evaluate how effective cannabidiol is when used alongside standard antipsychotic medications, which are commonly prescribed to manage symptoms of schizophrenia.

Participants in the study will receive either cannabidiol or a placebo in the form of hard capsules. These capsules are taken orally, meaning they are swallowed. The study will be conducted over a period of time, during which participants will continue their usual antipsychotic treatment. The goal is to see if adding cannabidiol can help improve recovery in individuals with early-phase schizophrenia. The study will monitor various aspects of participants' health and well-being, including their mental health symptoms, social and occupational functioning, and overall quality of life.

Throughout the study, researchers will also keep track of any changes in participants' mood, cognitive abilities, and any side effects they may experience. This will help determine the safety and tolerability of cannabidiol as an additional treatment. The study aims to provide valuable insights into whether cannabidiol can be a beneficial add-on therapy for people with schizophrenia, potentially enhancing their recovery and quality of life.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, informed consent is required. This means understanding the study's purpose and agreeing to participate.

    Eligibility is confirmed based on criteria such as age, diagnosis, and current medication stability.

  2. Step 2

    Randomization

    Participants are randomly assigned to receive either cannabidiol or a placebo. This process is double-blind, meaning neither the participant nor the researchers know which treatment is being administered.

  3. Step 3

    Medication administration

    Participants take cannabidiol capsules or placebo orally. The exact dosage and frequency are determined by the study protocol and are administered alongside the participant's regular antipsychotic medication.

  4. Step 4

    Regular assessments

    Throughout the study, regular assessments are conducted to monitor symptoms, social and occupational functioning, and quality of life.

    These assessments include various scales and questionnaires to evaluate mental health and overall well-being.

  5. Step 5

    Monitoring and safety checks

    Participants undergo regular safety checks, including physical examinations, vital signs monitoring, and laboratory tests.

    Any side effects or adverse events are closely monitored to ensure participant safety.

  6. Step 6

    Completion of the study

    The study concludes after a specified period, typically up to 12 months.

    Final assessments are conducted to evaluate the overall impact of the treatment on the participant's condition.

Who can join the trial?

8 criteria

  • The patient must give their informed consent, which means they agree to participate after understanding the study details.
  • The patient must have a diagnosis of schizophrenic psychosis according to a specific guideline called DSM-IV-TR.
  • The patient must be taking a stable dose of certain medications for at least two weeks before joining the study. These medications include amisulpride, aripiprazole, olanzapine, paliperidone, quetiapine, or risperidone.
  • The patient must be between the ages of 18 and 65, and can be either male or female.
  • The patient must have an initial PANSS total score of 75 or less. PANSS is a scale used to measure symptoms of schizophrenia.
  • Female patients who can have children must use a proper method of contraception to prevent pregnancy during the study.
  • The patient must have a Body Mass Index (BMI) between 18 and 40. BMI is a measure of body fat based on height and weight.
  • The patient must be fluent in either German or English.

Who cannot join the trial?

4 criteria

  • Individuals who do not have a diagnosis of remitted early phase schizophrenia. This means the person must have been diagnosed with schizophrenia that is in a stable or improved state.
  • Individuals who are not currently receiving antipsychotic maintenance treatment. This refers to ongoing medication or therapy to manage symptoms of schizophrenia.
  • Individuals who are not within the specified age range for the study. The study has specific age requirements that participants must meet.
  • Individuals who are part of a vulnerable population. This typically includes groups like children, pregnant women, or those unable to give consent.
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Investigated drugs

Cannabidiol is being studied as an additional treatment for schizophrenia. It is being tested to see if it can help improve recovery when used alongside standard antipsychotic medications. Cannabidiol is a compound found in cannabis plants, but it does not cause the "high" associated with marijuana. Researchers are interested in its potential benefits for mental health conditions like schizophrenia.

What is already known about the treatment

Cannabidiol – Cannabidiol is administered orally, typically in the form of oil or capsules. It is currently being studied in clinical trials as an add-on treatment for schizophrenia, particularly in the early phases of the condition. The main therapeutic indication is to enhance recovery in individuals with remitted early phase schizophrenia. At the molecular level, cannabidiol is believed to interact with the endocannabinoid system, potentially modulating neurotransmitter release and reducing psychotic symptoms. It is classified as a cannabinoid, a group of compounds found in cannabis plants.

Investigated diseases

Schizophrenia – Schizophrenia is a chronic mental health disorder that affects how a person thinks, feels, and behaves. It often begins in early adulthood and can cause symptoms such as hallucinations, delusions, and disorganized thinking. In the early phase, individuals may experience a remission of symptoms, where they temporarily improve or disappear. However, the disorder typically progresses with episodes of worsening symptoms. People with schizophrenia may also struggle with maintaining social relationships and employment. The condition requires ongoing management to help individuals lead more stable lives.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-517198-26-00Protocol codeCBD-ESPRITEstimated enrolment180 patientsSponsorZentralinstitut Fuer Seelische Gesundheit

sourced from the EU Clinical Trials Register and site verification

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© 2026 Clinical Trials EU – European Clinical Trials Information Network

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).