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Taking a daily probiotic supplement may temporarily improve sleep and vitality in people experiencing mild to moderate depression. Over an eight-week period, a specific bacterial strain offered rapid boosts to mental well-being, though the initial advantages leveled out as time went on. The findings were published in Experimental and Clinical Psychopharmacology.
Mood disorders are a leading cause of disability worldwide. People experiencing mild to moderate depressive symptoms are often managed in primary care medical settings rather than by specialized psychiatrists. Many of these individuals hesitate to start traditional antidepressant medications due to concerns that the side effects might outweigh the modest clinical benefits.
The human digestive tract hosts trillions of microorganisms that help digest food and regulate the immune system. These microbes also produce chemicals that communicate directly with the brain through a network called the gut-brain axis. For instance, certain gut bacteria manufacture precursors to serotonin, a chemical messenger that stabilizes mood. When the microbial balance in the digestive tract is disrupted, it can negatively influence mental health and physiological stress responses.
Researchers are exploring psychobiotics as an alternative or supplementary option for mood management. Psychobiotics are live bacteria that provide mental health benefits when ingested. A team led by Kelly M. Seamans, a researcher at the biotechnology company Novonesis in Ireland, wanted to see if a specific strain could relieve low mood. The strain, known as Bifidobacterium longum 1714, had previously shown promise in earlier trials for improving sleep quality and softening the biological response to stress.
The researchers designed a trial involving 168 adults between the ages of 18 and 70. All participants had mild to moderate depressive symptoms, which the team confirmed using standard psychological checklists. To isolate the effects of the bacteria, participants were excluded if they were currently taking antidepressants, sleep medications, or undergoing cognitive behavioral therapy.
The participants were randomly divided into two equal groups. One group took two capsules a day containing the active Bifidobacterium longum 1714 strain. The other group received identical placebo capsules containing inactive ingredients like corn starch.
Neither the researchers nor the participants knew who received the active supplement or the placebo until the trial concluded. This double-blind design helps prevent expectations from skewing the final results. The intervention lasted for eight weeks, with researchers evaluating the participants at the midpoint and the end.
The primary goal was to measure changes in overall depression severity. To do this, the researchers used the Beck Depression Inventory. This is a standard survey that asks participants to rate symptoms like sadness and loss of interest over the previous two weeks.
By the end of the eight weeks, both groups reported feeling substantially better than they did at the start of the study. The difference in overall depression scores between the probiotic group and the placebo group was not statistically significant at any point in the trial. The active bacteria did not provide a unique advantage for this primary mood metric.
While the primary mood scores did not diverge between the two groups, the researchers noted other changes during the first four weeks. At the trial’s midpoint, participants taking the probiotic experienced a greater decrease in a secondary survey of depressive symptoms compared to the placebo group. The probiotic group also reported much better sleep quality.
The sleep evaluations assessed factors like how long it takes to fall asleep and how often a person wakes up during the night. By week four, the probiotic group had shorter sleep latency, meaning they fell asleep faster than the control group. The total number of people classified as poor sleepers also dropped more sharply in the group taking the bacteria.
The probiotic group also reported higher scores in specific quality-of-life categories at week four. These categories included mental health, social role functioning, and vitality. Vitality refers to a person’s physical and mental energy levels, which often plummet during depressive episodes.
By the end of the eight-week study, most of these early advantages faded. The placebo group experienced continued improvements, effectively catching up to the probiotic group in sleep quality and most mood categories. The differences between the groups at week eight were not statistically significant for almost all measurements.
There was one exception to this convergence at the end of the trial. The probiotic group retained a measurable edge in self-reported vitality scores at week eight. The researchers noted that higher vitality scores correlated closely with lower overall depression scores across the study.
Throughout the study, the researchers monitored participants for adverse effects by conducting blood tests and checking vital signs. The probiotic was deemed safe, and there were no prominent differences in side effects between the active and placebo groups. Most reported health issues, such as minor gastrointestinal complaints, were typical for dietary supplements.
The strong response in the placebo group limits the ability to draw firm conclusions about the probiotic’s long-term effectiveness. In clinical trials for mild depression, participants often improve simply because they expect the treatment to work or because they are receiving regular attention from health professionals. It is possible that the bacteria provide a rapid initial benefit that is eventually matched by the natural course of healing and the placebo effect.
The study design also left a few lifestyle variables unmonitored. While the researchers recorded dietary and exercise habits at the beginning of the trial, they did not track these behaviors throughout the eight weeks. Unmeasured changes in a participant’s daily routine, such as exercising more frequently, could have influenced their mood and sleep.
The participant pool was also predominantly female. Hormonal fluctuations can heavily influence mood and energy levels, but the researchers did not track menstrual cycles or hormone therapy. Future trials could control for these variables by focusing on specific demographic groups or tracking biological markers more closely.
The study, “Effects of Bifidobacterium longum 1714 on Low Mood and Related Symptoms: A Randomized, Double-Blind, Placebo-Controlled Trial,” was authored by Kelly M. Seamans, Elaine Patterson, Caterina Holz, David Groeger, Jouni Junnila, Fergus Collins, Eileen F. Murphy, Katy Sorensen, and Timothy G. Dinan.
