Table 2

The mediation effect of gut microbiome on depressive symptoms via body mass index

Gut microbiota (exposure)Depressive symptoms (outcome)Total effect
β (95% CI)
Direct effect A
β (95% CI)
Direct effect B
β (95% CI)
Mediation effect
β (95% CI)
Mediated proportion (%)
Genus. Bifidobacterium Anhedonia–0.03 (–0.05 to –0.02)–0.09 (–0.13 to –0.05)0.05 (0.03 to 0.08)–0.01 (–0.00 to –0.01)14.14
Phylum. ActinobacteriaAnhedonia–0.04 (–0.06 to –0.02)–0.09 (–0.13 to –0.04)0.05 (0.03 to 0.08)–0.01 (–0.00 to –0.01)13.10
Genus. Bifidobacterium Depressed mood–0.03 (–0.05 to –0.02)–0.09 (–0.13 to –0.05)0.03 (0.01 to 0.06)–0.00 (–0.00 to –0.01)8.05
Phylum. ActinobacteriaDepressed mood–0.03 (–0.05 to –0.03)–0.09 (–0.13 to –0.04)0.03 (0.01 to 0.06)–0.00 (–0.00 to –0.01)8.31
Phylum. ActinobacteriaChanges in Appetite–0.04 (–0.06 to –0.01)–0.09 (–0.13 to –0.04)0.14 (0.11 to 0.17)–0.01 (–0.01 to –0.02)34.42
  • ‘Total effect’ refers the effect of gut microbiota on major depression, ‘direct effect A’ indicates the effect of gut microbiota on body mass index, ‘direct effect B’ indicates the effect of body mass index on major depression and ‘mediation effect’ indicates the effect of gut microbiota on major depression through body mass index. Total effect, direct effect A and direct effect B were derived by inverse variance weighted; mediation effect was derived by using the delta method.