A daily probiotic may help relieve depression and anxiety, new trial finds
A new randomised, placebo-controlled trial from the Netherlands, published in The British Journal of Psychiatry, has found that a multi-strain probiotic blend taken daily for eight weeks significantly reduced symptoms of mild-to-moderate depression and anxiety compared with placebo. The work adds strong new data to a growing body of research on the gut-brain axis.
Led by Leiden University Medical Center, the trial enrolled 200 adults who did not meet clinical thresholds for depression but scored in the mild-to-moderate range on the Beck Depression Inventory. Participants were randomly assigned to two arms: one received a daily blend of Lactobacillus and Bifidobacterium strains; the other received an identical-looking placebo.
After eight weeks, the probiotic group's Beck Depression Inventory score dropped on average by 28%; the placebo group dropped 12%. A similar gap was seen on anxiety scores: the probiotic group fell by 24%, the placebo group by 9%. The difference was statistically significant.
Lead author Prof Roel van Driel told Science Daily, "This is a large-scale early validation that goes beyond small pilot work." He said his team is planning a Phase 3 confirmatory trial with 1,000 participants next year.
The gut-brain axis is the two-way communication network between the gastrointestinal microbiome and the central nervous system. Operating via the vagus nerve, hormonal regulation and the immune system, this axis has been hypothesised for years to influence mood and stress responses. New studies are putting that hypothesis on firmer ground.
The Leiden team also analysed stool samples from participants. In the probiotic group, colonisation of Bifidobacterium longum and Lactobacillus helveticus rose significantly; blood cortisol levels in the same participants fell by an average of 17%. The team says the mood improvements may relate in part to a softer hormonal stress response.
Professor Edward Bullmore of the University of Cambridge, who was not involved in the trial, said the results were "plausible and promising" but did "not mean the general public should be taking a daily probiotic". He noted that the dose and strain combination were specific and that most retail probiotic products do not contain the same composition.
Experts also stress that probiotics should not be considered a replacement for antidepressant medication. The trial excluded cases of severe depression, and patients requiring pharmacotherapy were not assessed. Van Driel said, "This should be thought of as a supportive approach; in mild symptoms it could be a first-line option."
The side-effect profile and long-term commitment associated with current antidepressants remain a barrier for many patients. The efficacy of selective serotonin reuptake inhibitors (SSRIs) has long been debated; mild side effects and sexual dysfunction are common complaints. The probiotic side-effect profile in the trial appeared milder.
Next steps include comparing different strain combinations, longer follow-up and a more detailed look at mechanism. The team is also planning combination studies with prebiotic fibre enrichment. Van Driel said the results suggest that "something as simple as food could support mental health".
Read next
Why vitamin D deficiency turns far more dangerous when belly fat is involved
A large study of more than 5,500 adults over 50 found that abdominal obesity combined with vitamin D deficiency was linked to a 123% higher risk of death within six years. Researchers say the two conditions appear to feed into each other, creating a dangerous cycle rather than simply adding independent risks.
Can drinking orange juice every day really change your genes
New research suggests regularly drinking orange juice may influence the activity of thousands of genes tied to inflammation, blood pressure, metabolism and blood sugar control. Scientists suspect natural citrus compounds such as hesperidin, along with benefits to the gut microbiome, may be behind the effect.
Do weight-loss drugs really save money? Mostly only for high earners
New analysis finds that someone needs roughly £100,000 a year in discretionary income to actually come out ahead financially on grocery savings after paying for GLP-1 weight-loss medication. Researchers describe the pattern as a 'tax on being thin' that leaves most patients worse off financially, even as their health improves.
US recalls 1.6m dozen eggs as salmonella outbreak sickens dozens
Nearly 1.6 million dozen eggs have been recalled across the US south and south-west after being linked to a salmonella outbreak that has sickened nearly 100 people, one of the largest recorded foodborne illness incidents in recent US history. The FDA has classified the recall at its highest risk level.
Methadone clinics: what two years of looser US rules actually changed
It has been two years since US regulators relaxed the rigid rules governing methadone clinics that treat opioid addiction. Some clinics have used the new flexibility to ease access for patients, but many have changed little from their older, stricter routines.