Table 1.
Characteristics of included studies.
| Study | Study characteristics | Potential Confounders | N of Subjects | Results | |||||
|---|---|---|---|---|---|---|---|---|---|
| First author, Year | Cases | Controls | Potential Confounders | Cases | Controls | ||||
| Aarts et al. (5) | Microbiome Sample: ADHD cases were diagnosed based on DSM-IV symptoms using the Schedule for Affective Disorder and Schizophrenia for School Age Children |
Healthy participants & unaffected siblings of ADHAD patients & self-reported healthy volunteers | Not mentioned | N: 19 Age in years: 19.5(2.5) Males: 13 BMI: 23.8(4.1) |
N: 77 included:
Ages in years: 27.1 (14.3) Males: 41 BMI:23.0 (3.2) |
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| Aarts et al. (5) | FMRI Sample: from the above ADHD cohort follow up study: Children with ADHD no longer met the diagnostic criteria in adolescence or adulthood |
Healthy & unaffected participants | Not mentioned | N: 24 Age in years: 20.3(3.7) Males: 18 BMI:22.8(3.5) |
N:63 included:
Age in years: 21.3 (3.4) Males: 39 BMI:22.7(2.9) |
Decreased ventral striatal response for reward anticipation in Patients with ADHD vs. controls (t(85)=2.1, p=.038) | |||
| Aarts et al. (5) | Microbiome and Imaging Analysis: From the above ADHD cohort |
Healthy & unaffected participants | N:6 Age in Years:18.6(2.5) Males:4 BMI:22.1(4.4) |
N:22 included:
Age in Years: 21.1(3.3) Males: 13 BMI:23.4 (3.7) |
No significant decreased ventral striatal response for reward anticipation in Patients with ADHD vs. Controls (t(26)= 0.2) Predicted CDT relative abundance significant associated with reward anticipation responses in ventral striatum (standardized beta: -0.42, p= 0.048) |
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| Jiang et al. (6) | Juvenile Patients diagnosed with the Kiddle-SADS-Present and Lifetime Version (Kiddle-SADS-PL) Scale: semi-structured diagnostic interview conducted according to the DSM-IV classification system ADHD Symptom severity via parents CPRS |
Healthy neurotypical Control Group recruited via advertisement and assessed with a semi-structured clinical interview to exclude individuals with a physical illness | Excluded confounders: Children with dietary habits Use of probiotics or antibiotics during the 2 months prior sample collection Apparent gastrointestinal symptoms, depressive or anxiety symptoms, obesity, common childhood atopic diseases &/or history of current use of ADHD drugs |
N: 51 treatment naïve ADHD patients Age in Years: 8.47(0.47) Males:38 BMI:16.4 (2.02) |
N: 32 Age: 8.5(8.47) Males: 22 BMI:16.09(2.02) |
Significant decrease in the fractional representation of Faecalibacterium in children with ADHD vs. Controls Abundance of Faecalibacterium negatively associated with parental reports of ADHD Symptoms No significant difference in the alpha diversity between groups |
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| Prehn-Kristensen et al. (7) | All patients met the DSM-IV criteria for ADHD Measures: German translation of the Revised Schedule for Affective Disorder and Schizophrenia for School-Age Children: Present and Lifetime Version (K-SADS-PL) CCBCL; German ADHD rating scale (FBB-HKS) |
N:6 Patients fulfilled criteria for comorbid oppositional defiant disorder (ODD) N:10 Medicine for more than one year to treat ADHD Symptoms (9x Medikinet, 1x Equasym) N:9 medicine for at least 48h prior to sample |
N:14 Age in years: 11.9 (2.5) BMI:19.0(3.9) Males: 14 |
N:17 Age in Years:13.1(1.7) BMI:18.0(2.5) Males: 17 |
Alpha diversity significant decreased in ADHD patient vs. controls (Pshannon=.036) Beta diversity differed significantly between patients and controls (PANOSIM) 0.033, PADONIS =0.006, Pbetadisper =.002) |
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| Cheng et al. (8) | Diagnosed with DSM Criteria | N: 19099 | N:34194 | Desulfovibrio is associated with ADHD | |||||
| Wang et al. (9) | Patients with ADHD treated in the outpatient Department of a Child Psychiatry ADHD cases were diagnosed based on DSM-IV-TR trough structured interview based an K-SADS-E Dietary patterns through food frequency questionnaire |
Children without ADHD Dietary patterns trough food frequency questionnaire |
Excluded Confounders: Never taken any medications to treat ADHD; no psychiatric diseases or major physical illnesses No vegetarians or Patients who were currently taken probiotics or antibiotics |
N: 30 Age in Years: 8.4 (1.7) Weight(kg): 30.7(10.2) Males: 23 |
N:30 Age in Years: 9.3(2.2) Weight(kg): 35.6(10.6) Males: 18 |
Gut microbiota communities in ADHD patients showed a significantly higher Shannon Index p=.0378) and Chao Index (p=.0351)as the controls Simpson Index was significant lower in ADHD patients |
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| Stevens et al. (10) | Micronutrient Treatment group Cases diagnosed with ADHD via ADHD Rating Scale IV (ADHD-RS-IV) |
Placebo treatment Group Controls diagnosed with ADHD via ADHD Rating Scale IV (ADHD-RS-IV) |
Not mentioned | N:10 Age: 9.3(1.3) BMI:16.6(3) Males: 10 |
N:9 Age: 10.29(1.9) BMI:19.39(2.9) Males: 9 |
OTUs significantly increased in the treatment group and no mean change in the placebo group (p:0.05) low abundance of Bifidobacterium was associated with a low ADHD-IV-RS score, which is contradictory to the general trend observed in the pre-RCT and placebo groups. |
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| Casas et al. (11) | ADHD assessed trough German parent- completed SDQ (10years) and self-completed version of SDQ (15 years) | Medication not mentioned Reporting bias Controlled confounders: parental education, indoor factors, e.g. indoor smoking |
N:37 Male: 22 Hyperactivity/inattention
|
N:189 Male: 95 Hyperactivity/inattention
|
Early life bacterial diversity was inversely associated with hyperactivity/ inattention at age 10 [bacterial OTUs (medium vs low: aOR = 0.4, 95%CI = (0.2–0.8)) and Chao1 (medium vs low: 0.3 (0.1–0.5); high vs low: 0.3 (0.2–0.6)], fungal diversity was directly associated [Chao1 (high vs low: 2.1 (1.1–4.0)), Shannon (medium vs low: 2.8 (1.3–5.8)), and Simpson (medium vs low: 4.7 (2.4–9.3))] At age 15, only Shannon index was significantly associated with hyperactivity/inattention [bacteria (medium vs low: 2.3 (1.2–4.2); fungi (high vs low: 0.5 (0.3–0.9))] |
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CRPS, Conners Parent Rating Scales; BMI(SD): SD, standard deviation; Age(SD): SD, standard deviation; CBCL, Child Behavior Checklist; FBB-HKS, Fremdbeurteilungsbogen für hyperkinetische Störung; DSM-IV-R, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision; K-SAD-E, Schedule for affective disorder and schizophrenia for school- age children, epidemiologic version; SDQ, Strength and Difficulties Questionnaire.