Background. Anxiety and depression are becoming increasingly prevalent today and are often aggravated by day-to-day stresses. Because current management strategies are usually accompanied by unpleasant side effects, there is a need to look into alternative treatment regimens - such as prebiotics - that may provide equally effective anxiolytic and antidepressant effects.

Objective. Therefore, the study aims to determine the effect of a combined fructooligosaccharide (FOS) and galactooligosaccharide (GOS) supplemented diet on anxiety and depression levels in mice subjected to Unpredictable Chronic Mild Stress (UCMS).

Methods. Forty male BALB/C mice were subjected to UCMS under a pretest-posttest control group design where the treatment group received prebiotic supplementation throughout the study. Repeated measures ANOVA was run to evaluate between, within, and time interactions of the measured anxiety parameters using the light-dark box test, and depression parameter using the fur coat state assessment.

Results. Results show that (1) the FOS + GOS treatment did not give the treatment group an advantage over the control group during UCMS, (2) both groups grew more anxious and depressed over time, and (3) the treatment group grew more anxious with time in relation to control in terms of the total time spent in the light side.

Conclusion. These imply that the UCMS protocol was successful in inducing stress in mice, but the FOS + GOS regimen failed to provide anxiolytic and antidepressant effects on male BALB/C mice exposed to UCMS.