Table 1.

Summary of studies implicating dysbiosis in schizophrenia.

Study design	(Microbial richness/diversity)	Significantly more abundant taxa in schizophrenia		Significantly more abundant taxa in controls
aStudy group: 81 high-risk subjects (at least one first-degree relative with schizophrenia), 19 ultra-high risk subjects (defined by structured interview for prodromal syndromes), 69 healthy controls; all participants were 13–30 year-old Han Chinese individuals Exclusion criteria: GI and endocrine diseases, serious organ disorders, history of psychiatric disorders and corresponding treatment, use of medication within previous 3 months Experimental method: 16S rRNA gene sequencing from fecal samples	No significant difference between the three groups	Orders: Clostridiales, Lactobacillales, Bacteroidales Genera: Lactobacillus, Prevotella Species: Lactobacillus ruminis	Not reported
bStudy group: 64 schizophrenic patients, and 53 healthy controls; 18–65 year-old Han Chinese individuals Exclusion criteria: chronic disease in the last 3 months, use of medication within the last 6 months (including antibiotics and probiotics, but excluding antipsychotic medication) Experimental method: 16S rRNA gene sequencing from fecal samples	No significant difference	Phyla: Proteobacteria Classes: Gammaproteobacteria Orders: Aeromonadales, Fusobacteriales Families: Veillonellaceae, Prevotellaceae, Enterobacteriaceae, Succinivibrionaceae, Fusobacteriaceae, Lactobacillaceae	Genera: Succinivibrio, Megasphaera, Collinsella, Clostridium, Klebsiella, prevotella, Lactobacillus, Fusobacterium, Citrobacter, Acidaminococcus, Desulfovibrio, Phascolarctobacterium Species: Collinsella aerofaciens, Bacteroides fragilis, Prevotella stercorea, Lactobacillus mucosae, Bifidobacterium adolescentis	Phyla: Firmicutes Classes: Clostridia Orders: Clostridiales Families: Lachnospiraceae, Alkaligenaceae Genera: Blautia, Coprococcus, Roseburia, Streptococcus	Species: Roseburia faecis, Blautia producta, Collinsella plebeius, Bacteroides eggerthii
cStudy group: 63 schizophrenic patients, 69 healthy controls; most patients receiving antipsychotic medication; participants recruited from the First Affiliated Hospital of Chongqing Medical University Exclusion criteria: other physical and mental disorders; use of antibiotics, probiotics, and prebiotics within 1 months before sample collection Experimental method: 16S rRNA gene sequencing from fecal samples	Lower indices of both microbial richness and diversity in schizophrenic patients	Families: Veillonellaceae, Prevotellaceae, Bacteroidaceae, Coriobacteriaceae Genera: Megasphera, Akkermansia, Fusobacterium, Prevotella		Families: Lachnospiraceae, Ruminococcaceae, Enterobacteriaceae, Acidaminococcaceae, Rikenellaceae	Genera: Citrobacter, Blautia, Coprococcus, Lachnoclostridium Species: Bacteroides eggerthii, Bacteroides massiliensis, Collinsella stercoris, Haemophilus parainfluenzae
dStudy group: 25 outpatients with schizophrenia or schizoaffective disorder, 25 healthy controls; aged between 30–76; most schizophrenic patients were receiving antipsychotic medication Exclusion criteria: Other major psychiatric disorders, substance abuse, major neurological disorders Experimental method: 16S rRNA gene sequencing from fecal samples	No significant difference	Classes: Clostridia, Erysipelotrichi Orders: Clostridiales Genera: Anaerococcus, Haemophilus, Sutterella, Megasphera, Coprococcus, Blautia, Ruminococcus		Phyla: Proteobacteria Genera: Haemophilus, Sutterella Species: Haemophilus parainfluenzae
eStudy group: 16 schizophrenia patients and 16 controls; age 18-65; recruited from the Stanley Research Program Exclusion criteria: substance abuse, mental retardation, HIV infection, disorders affecting cognitive functioning Experimental method: Illumina sequencing of DNA extracted from throat swabs	Lower microbial richness in schizophrenic patients	Phyla: Firmicutes Genera: Bifidobacterium, Lactobacillus Species: Lactobacillus gasseri, Catenibacterium mitsuokai, Lactobacillus salivarius, Bifidobacterium pseudocatenulatum, Streptococcus gordonii, Streptococcus thermophiles		Phyla: Bacteroidetes, Actinobacteria
fStudy group: 28 first psychotic episode patients and 16 controls from Finland; most patients were receiving antipsychotic medication for a median of 20 days Exclusion criteria: substance-induced psychosis and psychosis due to a general medical conditions Experimental method: 16S rRNA gene sequencing from fecal samples	Not reported	Families: Lactobacillaceae, Halothiobacillaceae, Brucellaceae, Micrococcineae Genera: Lactobacillus, Bifidobacteria, Tropheryma, Halothiobacillus, Saccharophagus, Ochrobactrum, Deferribacter, Halorubrum		Families: Veillonellaceae Genera: Bacteroides, Ruminococcaceae, Gallionella, Anabaena, Nitrosospira

^aHe et al. (16).

^bShen et al. (17).

^cZheng et al. (18).

^dNguyen et al. (19).

^eCastro-Nallar et al. (20).

^fSchwarz et al. (21).