Recently, cognitive behavioral therapy has been validated as an effective psychological treatment for depression. However, efficacy rates of treatment still indicate the need for improvement. Recent evidence indicates that changes in gastrointestinal health can have positive or negative effects on mental health. This trial investigates whether administration of Ecologic® Barrier is effective in reducing levels of depression in a population of depressed adults. Depressive symptoms will be measured at baseline and after 8 weeks of intervention, and changes in levels of depression between the probiotic and the placebo group will be compared. This study is done in collaboration with the University of Technology, Sydney, Australia.