The goal of this clinical trial is to learn if probiotics work to prevent or reduce metabolic side effects caused by antipsychotic medication in adults.

The main question it aims to answer is:

Do probiotics reduce weight gain, blood sugar levels, and blood fat levels in people using antipsychotics?

Researchers will compare a probiotic (Ecologic® Barrier) to a placebo (a look-alike powder without active bacteria) to see if the probiotic is effective.

Participants will:

Take either probiotics or a placebo daily for 12 weeks (3 months) Dissolve two sachets in water and drink them each morning Visit the clinic (or receive home visits) four times: at the start, after 6 weeks, and after 12 weeks, plus an initial screening visit Undergo physical measurements (e.g., weight, blood pressure), complete questionnaires, and perform a cognitive test at specific visits Provide blood samples and stool samples at the beginning and end of the study Complete two 3-day food diaries during the study

Antipsychotic medications such as olanzapine, quetiapine, clozapine, and risperidone are widely used for the treatment of psychotic and mood disorders. Although effective, these medications are frequently associated with adverse metabolic effects, including weight gain, increased blood glucose levels, and dyslipidemia. These side effects can negatively impact physical health and increase the risk of cardiovascular disease and diabetes.

Emerging evidence suggests that the gut microbiome may play a role in metabolic regulation and that modulation of gut microbiota through probiotics could mitigate antipsychotic-induced metabolic disturbances. Probiotics are live microorganisms that, when administered in adequate amounts, may confer health benefits by improving gut barrier function and influencing metabolic processes.

This study is a randomized, double-blind, placebo-controlled clinical trial designed to investigate the efficacy and safety of a multispecies probiotic formulation (Ecologic® Barrier) in preventing or reducing metabolic side effects in patients initiating treatment with antipsychotic medication. A total of 112 participants will be enrolled and randomly assigned to receive either the probiotic or a placebo for a duration of 12 weeks.

The investigational product consists of a powder formulation containing nine bacterial strains, administered as two sachets dissolved in water once daily in the morning. The placebo consists of an inert powder (e.g., maize starch and maltodextrin) with identical appearance and administration schedule. Participants, investigators, and study personnel will remain blinded to treatment allocation throughout the study.

Participants will continue their standard psychiatric treatment, including antipsychotic and/or mood-stabilizing medication, with minimal changes where possible. Concomitant use of additional psychotropic medications such as a second antipsychotic, lithium, or antiepileptic drugs is permitted.

Study procedures include baseline, interim (6 weeks), and end-of-study (12 weeks) assessments. These assessments involve physical measurements (e.g., body weight, waist and hip circumference, blood pressure), laboratory analyses of metabolic parameters using blood samples, and stool sample collection for microbiome-related analyses. In addition, participants will complete validated questionnaires assessing quality of life, eating behavior, and gastrointestinal symptoms, as well as cognitive testing at baseline and study completion.

Dietary intake will be monitored using two 3-day food diaries (pre-intervention and prior to the final visit) to account for potential dietary influences on metabolic outcomes and gut microbiota.

The primary objective is to evaluate whether probiotic supplementation reduces antipsychotic-induced metabolic disturbances compared to placebo. Secondary objectives include assessing safety and tolerability, as well as exploring changes in gastrointestinal symptoms, cognitive functioning, and potential microbiome-related mechanisms.

The total study duration per participant is approximately 3 months, with an additional optional one-month post-study probiotic use. After study completion, treatment allocation will be unblinded. Participants will be monitored throughout the study for adverse events, with particular attention to gastrointestinal symptoms, which are expected to be mild and transient.

This study aims to provide further evidence on the role of probiotics as a low-risk, adjunctive intervention to improve metabolic health in patients treated with antipsychotic medication.

Inclusion Criteria:

1. About to start, or having started within the last 8 weeks, antipsychotic treatment with olanzapine, quetiapine*, clozapine or risperidone for treating psychosis

2. Aged between 18 - 65

3. No exposure to these four antipsychotic medications for longer than one week continuously in the last 6 months (except starting the treatment with the current medication 8 weeks prior to the inclusion)

4. The participant understands the study and is able to provide written informed consent.

   • Quetiapine prescribed in a low dose for use as a sleep aid does not apply

Exclusion Criteria:

1. Critically ill patients (e.g. ICU), diagnosed comorbid eating disorders, chronic GI-disorders, disorders of the liver or pancreas, pre-existing diagnosed diabetes mellitus or metabolic syndrome
2. Current use of medications known to target metabolism or weight (e.g, diabetes medication and GLP-1 agonists, proton pump inhibitors and diuretics/beta blockers) or use of antibiotics or probiotics (such as Yakult, Activia, or other probiotic supplements containing ≥10⁹ CFUs) in the past 4 weeks
3. Pregnancy or breastfeeding
4. Inability to follow the intervention or other conditions that according to the investigator might interfere with the evaluation of the study objectives as judged by the treating physician