title: A double-blind, randomized, placebo-controlled trial of Lactobacillus helveticus and Bifidobacterium longum for the symptoms of depression.
abstract: OBJECTIVE
  This trial investigated whether probiotics improved mood, stress and anxiety in a sample selected for low mood. We also tested whether the presence or severity of irritable bowel syndrome symptoms, and levels of proinflammatory cytokines, brain-derived neurotrophic factor and other blood markers, would predict or impact treatment response.
  
  
  METHODS
  Seventy-nine participants (10 dropouts) not currently taking psychotropic medications with at least moderate scores on self-report mood measures were randomly allocated to receive either a probiotic preparation (containing Lactobacillus helveticus and Bifidobacterium longum) or a matched placebo, in a double-blind trial for 8 weeks. Data were analysed as intent-to-treat.
  
  
  RESULTS
  No significant difference was found between the probiotic and placebo groups on any psychological outcome measure (Cohen's d range = 0.07-0.16) or any blood-based biomarker. At end-point, 9 (23%) of those in the probiotic group showed a ⩾60% change on the Montgomery-Åsberg Depression Rating Scale (responders), compared to 10 (26%) of those in the placebo group ([Formula: see text], p = ns). Baseline vitamin D level was found to moderate treatment effect on several outcome measures. Dry mouth and sleep disruption were reported more frequently in the placebo group.
  
  
  CONCLUSIONS
  This study found no evidence that the probiotic formulation is effective in treating low mood, or in moderating the levels of inflammatory and other biomarkers. The lack of observed effect on mood symptoms may be due to the severity, chronicity or treatment resistance of the sample; recruiting an antidepressant-naive sample experiencing mild, acute symptoms of low mood, may well yield a different result. Future studies taking a preventative approach or using probiotics as an adjuvant treatment may also be more effective. Vitamin D levels should be monitored in future studies in the area. The results of this trial are preliminary; future studies in the area should not be discouraged.
authors.affiliation: 1 Department of Psychology, University of Canterbury, Christchurch, New Zealand.|2 School of Psychology, Early Years and Therapeutic Studies, University of South Wales, Pontypridd, UK.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Romijn
authors.affiliation: 1 Department of Psychology, University of Canterbury, Christchurch, New Zealand.
authors.forename: Julia J
authors.initials: JJ
authors.lastname: Rucklidge
authors.affiliation: 1 Department of Psychology, University of Canterbury, Christchurch, New Zealand.
authors.forename: Roeline G
authors.initials: RG
authors.lastname: Kuijer
authors.affiliation: 3 Department of Psychological Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: Chris
authors.initials: C
authors.lastname: Frampton
mesh_terms: D000328:Adult; D000339:Affect; D001007:Anxiety / Q000178:diet therapy*; D000069978:Bifidobacterium longum; D003863:Depression / Q000178:diet therapy*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D052198:Lactobacillus helveticus; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D019936:Probiotics / Q000008:administration & dosage / Q000494:pharmacology*; D012042:Registries; D013315:Stress, Psychological / Q000178:diet therapy*
keywords: Probiotic; anxiety; gut; immune function; inflammation; mood; stress; vitamin D