Table 2.

Summary of articles that assessed adverse events in the studied population.

Author, Year	Number of Patients with Psychobiotics	Number of Adverse Events in Patients with Psychobiotics	Reported Adverse Events	Conclusion on Probiotic Safety
Dickerson F et al., 2014 [67]	33	0	Not reported	One serious adverse event occurred in the probiotic group, but none were directly related to the product.
Romijn et al., 2017 [38]	40	63	Constipation, appetite changes, nausea, weight gain, dry mouth, abdominal pain, anxiety, headache, rash, blurred vision, and sleep disruption.	Three serious adverse events occurred during the trial, which were associated with the placebo group. There were no serious adverse events in the probiotic group.
Pinto et al., 2017 [74]	22	4	Rhinitis, constipation.	Of 18 reported adverse events, only 4 were related to the supplied probiotic product.
Rudzki et al., 2018 [77]	30	14	Headache, diarrhea, and flatulence.	No serious adverse events occurred; moreover, patients with gastrointestinal events had irritable bowel syndrome, which could have contributed to these manifestations.
Dickerson F et al., 2018 [70]	26	75	Gastrointestinal, metabolic and endocrine, musculoskeletal, sensory alterations, cardiovascular and respiratory.	The probiotic was well tolerated by participants, and there were no withdrawals from the study related to the product. The authors did not detail the specific type of adverse event and whether these were directly related to probiotic consumption.
Majeed M et al., 2018 [48]	20	0	Not reported.	No adverse events related to probiotic intake occurred during the study period.
Ghorbani Z et al., 2018 [49]	20	3	Nausea and bloating.	The adverse events that occurred were not serious and, therefore, did not lead to any participant withdrawing from the study. There were no differences in the rate of adverse events between groups.
Miyaoka T et al., 2018 [50]	20	3	Neurological and dermatological.	The adverse events presented by participants were not detailed. No serious adverse events related to the probiotic were reported.
Kazemi A et al., 2018 [51]	74	13	Gastrointestinal issues, fever, body pain, and increased appetite.	No serious adverse events related to the consumption of probiotics or prebiotics were reported.
Vaghef E et al., 2021 [46]	22	5	Gastrointestinal discomfort.	No serious adverse events occurred. The adverse events that occurred were resolved in less than two weeks.
Kobayashi Y et al., 2019 [62]	61	0	Not reported.	No adverse events related to probiotic intake occurred during the study period.
Hwang Y et al., 2019 [61]	50	7	Dizziness, stomach aches, headaches, gastritis, erectile dysfunction, and seborrheic dermatitis.	One of the adverse events reported in the probiotic group was classified as serious, and the participant withdrew to receive treatment. Most adverse events were classified as mild.
Gualtieri et al., 2020 [72]	65	0	Not reported.	No adverse events were observed in the study.
Xiao et al., 2020 [58]	40	0	Not reported.	No adverse events were observed in the study.
Sacarello et al., 2020 [39]	45	2	Reduced appetite and mood disorder.	The reported adverse events were not related to the product supplied in the study.
Zhang et al., 2021 [41]	38	0	Not reported.	No adverse events were observed in the study.
Eskandarzadeh S et al., 2021 [73]	24	2	Dizziness and itching.	No serious adverse events leading to participant withdrawal were reported.
Haghighat N et al., 2021 [79]	25	1	Headache.	No serious adverse events occurred, and the one that occurred in the probiotic group was not directly related to the administration of the product.
Regiada L et al., 2021 [80]	27	7	Burping, bloating, increased frequency of bathroom visits, acne, anxiety, and insomnia.	No serious adverse events occurred. It is not specified whether the events were directly related to the intake of psychobiotics.
Jamilian H et al., 2021 [64]	26	0	Not reported.	No adverse events were observed in the study.
Asaoka et al., 2022 [60]	55	1	Constipation.	Three adverse events (including constipation) occurred; however, it is concluded that they were not related to probiotic consumption.
Vaghef E et al., 2023 [47]	22	5	Flatulence and soft stools.	No serious adverse events leading to participant withdrawal were reported.
Nikolova et al., 2023 [40]	24	14	Nausea, diarrhea, indigestion, constipation, reflux, heartburn, stomach pain, and burping.	There were no serious adverse events, nor treatment discontinuation associated with this cause. Nausea and indigestion only occurred in the probiotic group.
Freijy T et al.,2023 [81]	63	22	Bloating, gas, abdominal discomfort, changes in bowel movements, and headaches.	The treatment was well tolerated and caused few adverse events. No adverse events led to withdrawal from the study.