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Table 1 Characteristics of included studies

From: Erratum to: The effects of probiotics on depressive symptoms in humans: a systematic review

Reference Sample characteristics Strain Study design Duration of intervention Measurement Key findings and conclusions
Akkasheh et al. [34] 40 MDD patients. Age 20–55 years Lactobacillus acidophilus, L. casei, and Bifidobacterium bifidum Double-blind, randomized, placebo-controlled trial 8 weeks BDI Consumption of probiotic supplement improved BDI scores
Benton et al. [30] 124 healthy humans. Avg. age 62 years L. casei Double-blind, randomized, placebo-controlled trial 3 weeks POMS, self-rated mood No effect of probiotic on POMS results. Consumption of probiotic-containing yogurt improved self-reported mood of those whose mood was initially poor
Chung et al. [32] 36 healthy humans. Age 60–75 years L. helveticus Double-blind, randomized, placebo-controlled trial 12 weeks PSS, GDS-SF, DST, SRT, VLT, RVIP, Stroop Task No significant effects of probiotics on the PSS, GDS-SF. Consumption of probiotics did improve DST, SRT, VLT, RVIP, and Stroop Tasks scores
Gruenwal et al. [36] 34 adults suffering from stress or exhaustion. Mean age 44 years L. acidophilus and B. bifidum and longum Pre- and post-intervention assessment 6 months PNQ, EWL Subjects’ general condition improved by 40.7%. 73% of participants rated the effect of treatment as “good” or “very good”
Hilimire et al. [38] 710 young adults. Mean age 19 years Unknown Self-report questionnaires on fermented food consumption, neuroticism and social anxiety N/A BFI, SPAI-23 Consumption of fermented foods containing probiotics was negatively associated with symptoms of social anxiety and interacts with neuroticism to predict social anxiety symptoms. Those at higher genetic risk for social anxiety disorder (indexed by high neuroticism) show fewer social anxiety symptoms when they consume more fermented foods
Marcos et al. [37] 136 healthy students. Age 18–23 years L. casei Prospective, randomized, controlled, parallel study 6 weeks STAI No significant effects of probiotics on anxiety levels. Probiotics did modulate lymphocyte and CD56 cell counts
Messaoudi et al. [28] 55 healthy Caucasians. Mean age 43 years L. helveticus and B. longum Double-blind, randomized, controlled, parallel study 30 days HADS, HSCL-90, PSS, CCL Consumption of probiotics reduced global severity index of the HSCL-90 due to lower somatization, depression, and anger-hostility and also reduced HADS global scores. Consumption of probiotic reduced self-blame score on CCL and increased focus on problem solving. No effect on PSS
Messaoudi et al. [35] Sub-population of above sample of 25 with lowest UFC levels L. helveticus and B. longum Double-blind, randomized, controlled, parallel study 30 days HADS, HSCL-90 Consumption of probiotics reduced HADS and HSCL-90 scores
Rao et al. [31] 35 CFS patients. Age 18–65 years L. casei Double-blind, randomized, placebo-controlled pilot study 2 months BDI, BAI Consumption of probiotics significantly improved BAI scores. No effect on BDI scores
Steenbergen et al. [33] 40 non-smoking healthy young adults. Mean age 20 years B. lactis and L. acidophilus, brevis, casei, lactis, and salivarius Triple-blind, randomized, placebo-controlled, pre- and post-intervention assessment 4 weeks LEIDS-r Consumption of multispecies probiotic significantly reduced overall cognitive reactivity to depression (in particular aggressive and ruminative thoughts)
  1. MDD major depressive disorder, BDI Beck Depression Inventory, POMS profile of mood states scale, PSS perceived stress scale, GDS-SF geriatric depression scale, DST digit span test, SRT story recall test, VLT verbal learning test, RVIP rapid visual information-processing, PNQ psychological-neurologic questionnaire, EWL list of adjectives, BFI big five inventory, SPAI-23 social phobia and anxiety inventory, STAI state-trait anxiety inventory, HADS Hospital Anxiety Depression Scale, HSCL-90 Hopkins symptom checklist, CCL coping checklist, UFC urinary free cortisol, BAI Beck Anxiety Inventory, LEIDS-r Leiden index of depression sensitivity, fMRI functional magnetic resonance imaging