Final

The Effectiveness of Multi-Strain Probiotic Over a Probiotic with Five or Less Strains in Decreasing Major Depressive Disorder

Dr Judy Drago

Northwestern State University

PSYC 2430 Introduction to Experimental Methodology

Instructor

Due Date

Abstract

Major Depressive Disorder (MDD) has been associated with disruptions in gut microbiota, wherein specific bacterial strains play a crucial role in mood regulation. Existing research has demonstrated a link between depressive symptoms and altered gut flora (Barandouzi et al., 2020); however, the comparative effectiveness of multi-strain probiotics versus those containing fewer strains remains understudied. This randomized controlled study proposes to evaluate whether a 20-strain probiotic yields greater reductions in depressive symptoms than a probiotic with five or fewer strains. A total of 150 adults, aged 18 to 65, diagnosed with MDD, will be randomly assigned to either the multi-strain or low-strain probiotic group. Depression severity will be measured at baseline, week 4, and week 8 using the Beck Depression Inventory-II (BDI-II). It is hypothesized that the multi-strain group will show a significantly larger decrease in BDI-II scores. This research aims to fill a gap in current knowledge by identifying optimal probiotic formulations for alleviating depressive symptoms, thus offering a non-pharmacological and potentially safer alternative for individuals who either cannot or prefer not to use antidepressant medication. Findings may have implications for clinical practice, policy development, and future research on the gut-brain axis.

Key Words: gut microbiota, depression, probiotics

NOTE: YOUR ABSTRACT SHOULD NOT BE LONGER THAN 250 WORDS. KEEP IT SHORT AND TO THE POINT.

The Effectiveness of Multi-Strain Probiotic Over a Probiotic with Five or Less Strains in Decreasing Major Depressive Disorder

Understanding the relationship between [Independent Variable – gut microbiota] and [Dependent Variable -depression] is crucial for those who suffer from depression but do not wish to take antidepressants or have other medical conditions that make the medication contraindicated for treating depression. Fortunately, prior research has explored and found a relationship between gut microbiota and depression. Individuals with depression exhibit distinct gut microbiota profiles compared to non-depressed individuals. Barandouzi et al. (2020) found that depressed individuals have a high amount of Actinobacteria and Fusobacteria phyla (proinflammatory species of bacteria) and a low rate of other important bacteria. Inflammation of the gastrointestinal (GI) tract creates stress. Although the mechanism by which unhealthy gut bacteria impact mood is unclear, we do know that the gut connects directly with the brain via the gut-brain axis, a connection first reported in a study on mice. The brain-gut axis allows bidirectional communication between the gut and brain via neural, endocrine, and immune pathways (Mayer et al., 2014).

Previous studies have investigated various probiotics in relation to Major Depressive Disorder. What is missing in the literature is information on the effectiveness of different mixtures of probiotics that include multiple strains verses probiotics with five or fewer bacterium types.

Begin your literature review by discussing your first article summary [Summarize key findings from the article that are relevant to your hypothesis]

Carabotti et al. (2015) suggest the main mechanisms of the bidirectional brain-gut-microbiota axis is that gut-to-brain communication influences the production, release, and reuptake of neurotransmitters and neurotrophic factors (BDNF). Communication from the brain to the gut microbiota influences intestinal mucus production, motility and permeability, and immune function.

Insert your second article summary (Author, Year): [Summarize key findings relevant to your hypothesis]

In a randomized controlled exploratory trial, Wallace and Milev ( 2021) recruited 10 participants ( 7 females and 3 males, ages 18-65) via newspaper and website, from Kingston, Ontario. The one inclusive criterium was a diagnosis of Major Depressive Disorder (MDD). The purpose of the study was to examine the role of probiotics in decreasing symptoms of MDD and in improving sleep quality. Participants took a probiotic supplement containing Lactobacilus Helveticus R0052 and Bifidobacterium longum R0175 3 x 109 (3 billion colony-forming units, CFU, of live bacterial cells) per dose, once a day for 8 weeks. Clinical symptoms of depression were measured using a battery of clinical scales and self-report questionnaires (CAN-BIND protocol). Baseline data was taken and then measured again at week 4 and week 8. Significant improvement was measured in week 4 and sustained at week 8. These findings supported other studies on probiotics for decreasing MDD. Due to the low participant rate, it is suggested that a much larger study be conducted.

Insert your third article summary (Author, Year): [Summarize key findings relevant to your hypothesis]

Our understanding of the effectiveness of probiotics is increasing with each additional study on the relationship between healthy gut microbiota and decreased depression in individuals suffering from depression (Ng, et al., 2018; Kazemi et al., 2019; Wallace and Milev, 2021; and Sikorska et al., 2023). However, there are some limitations in research on this topic. One limitation in research is the variability in probiotic strains and dosages (Wallace and Milev, 2021), i.e., researchers are studying many forms of gut microbiota to determine their effect on depression and other mood disorders, but studies to date tend to focus on one or two or three strains of bacteria, and this has created a gap in the literature regarding probiotics using multiple strains and higher dosages of probiotics. Is a 20-strain, probiotic more effective than a 2-strain probiotic in decreasing MDD, or is it one or two specific gut bacteria that is responsible for the decrease in depression? From an economic perspective, the higher the number of bacterial strains that exist in a probiotic solution, the greater the cost, which may hinder those with MDD from taking probiotics. However, the ability to identify the right combinations of probiotics seems more likely with multi-strain probiotics. Accordingly, this study will compare the effectiveness of probiotics with 20 strains of microbes with a probiotic with 5 or fewer strains. Therefore, this study will examine the relationship between two levels of probiotics (IV) and depression (DV]. The following hypotheses will be tested:

· H1 (Alternative Hypothesis): Multispecies probiotic bacteria will be more effective in reducing depression than probiotics with 5 or fewer strains of bacteria.

· H0 (Null Hypothesis): There will be no difference between the effects of multi-strain probiotics and probiotics with 5 or fewer strains in reducing depression.

Next, explain how your research will contribute to knowledge on your topic by filling a gap, confirming previous studies, or providing new insight. What, if any, implications your research will have on applications, policy, practices, or theoretical advancements?

This research will (1) contribute to the growing body of knowledge by confirming the effectiveness of probiotics in the treatment of depression and (2) help to close the gap on the most efficient probiotic combinations in the treatment of this disorder. The findings from this study may have implications for relevant applications for practice, and or theoretical advancements.

Method

Participants

A total of 150 participants, males, and females, ages 18-65, with a diagnosis of Major Depressive Disorder (MDD) will be recruited for this study. The Inclusive criteria is a confirmed diagnosis of MDD. The exclusion criteria include current use of antidepressant medication, diagnosis of other mental health disorders, use of probiotics in the past year, and any gastrointestinal disorders that might interfere with probiotic absorption.

Participants will be recruited by placing ads on social media platforms and flyers strategically placed in mental health clinics, hospital waiting areas, and other facilities as permitted by the facility. Once interest is generated in participating in the study and names are collected, a simple random sample will be chosen by pulling a name from a closed box with an opening just large enough to reach in and pull a name from the box. After each name is chosen, the box will be shaken to remix the names.

Design

This study will be a randomized controlled experimental design (see Table 6.1 Overview of Sampling Techniques) with a between-groups structure in which participants will be randomly assigned to one of the two treatment conditions. The independent variable (IV) is the type of probiotic supplement (multi-strain vs. single-strain probiotics) and the dependent variable (DV) is the severity of depression, as measured by a standardized depression assessment scale

Participants will be randomly assigned to one of two treatment levels:

· Multi-strain probiotic group (20 strains of probiotics)

· Low-strain probiotic group (5 or fewer strains of probiotics)

Operational Definitions These italicized level three headings help but are not required. They are added to help you see the parts of a good Method section.

· Independent Variable (IV): Defined as the number of bacterial strains in the probiotic supplement, operationalized as a multi-strain probiotic supplement (20 strains) versus a low-strain probiotic supplement (5 strains or fewer).

· Dependent Variable (DV): Measured using the Beck Depression Inventory-II (BDI-II), where higher scores indicate greater depressive symptomatology.

Instruments

To obtain a baseline and repeated assessments at weeks 4 and 8, the Beck Depression Inventory-II (BDI-II) will be used the BDI-II is a 21-question self-report measure of the severity of depressive symptoms. Each question is scored from 0 – 3. Higher scores indicate a higher level of depression. The BDI-II has demonstrated strong reliability (Cronbach’s alpha[measures the internal consistency of the scale] ranged from 0.83 to 0.96 and test-retest reliability ranged from 0.73 to 0.96 (Wang and Gorenstein, 2013, p. 416). Convergent and divergent validity is positive, yielding a positive correlation with the Center for Epidemiologic Studies Depression Scale (r=0.69) and the Hamilton Rating Scale for Depression (r = .80, Gebrie, 2018).

Procedure

All procedures will be conducted in the order they appear in this proposal.

Informed Consent: On the day of the study, the participants will receive an informed consent form detailing the study’s purpose, procedures, potential risks, confidentiality, and their right to withdraw from the study at any time. Participants will be required to sign the consent form before they are accepted for participation in the study.

Pre-Assessment: Once the consent form is signed, each participant will complete the BDI-II to obtain a baseline assessment of depression

Randomization and Intervention: Once the assessment is completed. Participants will be randomly assigned to either the multi-strain probiotic group (Group A) or the low-strain probiotic group (Group B). Both groups will take one probiotic capsule daily for 8 weeks. Depending upon the group assigned to, participants will receive an 8-week supply of the probiotic multi-strain or probiotic single-strain. They will also receive an 8-week tracking sheet where they will list the time they take the probiotic each day. They will also be informed not to double the probiotic dose if they forget to take it. They should simply place an “X” on their track sheet for the day they did not take the probiotic

Post-Assessment: Depression severity and gut health will be reassessed in week 4 and week 8 using the same instrument. Participants will take the assessment online. An email reminder will be sent at the beginning of week 4 and 8 and midway through week 4 and 8.

Follow-Up : One month after the study ends, patients will be contacted via email and provided an online link where they will complete an online survey that focuses on the sustained effects of the probiotics on depression. They will also be given a telephone number to contact the researcher with any questions they may have.

Debriefing: Approximately two weeks after the Follow-Up, participants will receive a debriefing statement, via email, repeating the study’s purpose and providing the findings.

Data Analysis: ( The following information is just for your information. You are not expected to complete this part of the proposal)

Data will be analyzed using the Statistical Program for Social Sciences (SPSS). Descriptive statistics will summarize demographic information (age, sex) and baseline measure for depression assessed with the BDI-II.

· Hypothesis Testing: An independent samples t-test will be conducted to compare depression scores between the two groups at week 8.

· Repeated-Measures ANOVA will be used to assess changes in depression severity over time (baseline, week 4, and week 8).

· Effect Size: Cohen’s d will be calculated to determine the magnitude of the effect (Remember that the p-value tells you if a relationship is statistically significant. Well, the effect size, Cohen’s d, indicates how meaningful a difference or relationship is, i.e., a larger effect size would indicate a more substantial impact of probiotics on depression symptoms. A small effect size would indicate they are less substantial.impact).

Ethical approval will be obtained from the Institutional Review Board (IRB) at Northwestern State University before data collection begins. Participants will be assigned ID numbers to maintain anonymity, and data will be securely stored in an encrypted database.

References

Barandouzi, Z., Starkweather, A., Henderson, W., Gyamfi, A., & Cong, X. (2020). Altered

Composition of Gut Microbiota in Depression: A Systematic Review.  Frontiers in Psychiatry, 11.