The gut microbiome is essential for overall health and well-being ^1–4, and research shows that this important system is altered in children with neurodevelopmental disorders ^5–23 . One function of the gut microbiome is communication with the brain via the gut-brain axis, which allows for two way communication between the gut and the brain, and can impact cognitive function, brain physiology and behaviour ^24–28.  This communication appears to play a large role in normal brain development and neurodevelopmental disorders.

The impacts of the gut-brain axis on development and neurodevelopmental disorders

At both extremes of life, in infancy and old age, the gut microbiome is characteristically different from that of the adult ^25,29–31. Research indicates that gut dysbiosis, either in early childhood or in the elderly, significantly increases the likelihood of brain dysfunction ²⁷. While little is known about the specific role the gut microbiome plays in normal brain development and to what extent it plays in neurodevelopmental disorders, we do know that the gut and brain are formed from the same tissue in-utero and work closely together throughout one’s lifetime, influencing each other through the gut-brain axis ^24,26,32.

^{Figure from Cryan et al., 2019: Timeline of the changes in the microbiome across the lifespace, from birth to old age}

Early childhood is a period of significant behavioural, immune and biological development, where a relationship between the gut microbiome and the brain is thought to play an instrumental role ^33–37.  The influence of the gut microbiota during neurodevelopment appears to be essential for normal brain development and maturation ^20,37–40. Research suggests there are “critical periods” for the effects on the brain to take place upon microbe exposure ^2,26,41–45. It has been hypothesized that during these critical periods, the gut microbiota are highly influential concerning neurodevelopment ^{12,25,27,46–49}. Research indicates a correlation between childhood microbiota composition and behavioural temperament, functional activity/connectivity in the brain, and cognitive function ^25,50–53. While this would suggest a clear link between gut microbiota and neurodevelopmental disorders, this relationship is correlative rather than causal ²⁶. More clinical research is needed to understand whether changes in the gut microbiome are cause, consequence or unrelated to neurodevelopmental diseases and whether restoring the gut microbiome to a healthy state can resolve these conditions.

Gut microbiota impacts on brain development

It has been suggested that this abnormal gut development may impact cognitive development and programming of the immune system by disrupting critical physiological processes during brain development ^20,33,37,39. In children with ASD, GI symptoms have been reported to be strongly correlated with the severity of autistic-related behaviours ^{8,11,12,19,59–62}, providing support for the role the gut microbiome may play in this neurodevelopmental disorder.

The role of the gut microbiome in neurodevelopmental disorders may be tied to the alteration in neurotransmitters created in the gut. Studies have shown that multiple pathways related to neurotransmitter biosynthesis (creation) are significantly depleted in the gut microbiome of children with ASD compared with TD children, which may have profound functional consequences on the psychiatric abnormalities in ASD ^11,15,20,63. It is possible that altered production of microbial metabolites, precursors to neurotransmitters, may exacerbate ASD symptoms and may provide a possible mechanism underlying the genetic susceptibility of ASD  ^{8,11,15,20,64}.

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References: 1. Belkaid, Y. & Hand, T. W. 2014, 2. Rutsch, A. et al. 202, 3. Vatanen, T. et al.  2016, 4. Wilson, B. C. et al. 2019, 5. Coretti, L. et al. 2018, 6. De Angelis, M. et al. 2013, 7. De Angelis, M. et al. 2015, 8. Ding, X. et al. 2020, 9. Finegold, S. M. et al. 2010, 10. Huang, H. et al. 2019, 11. Huang, M. et al. 2021, 12. Jendraszak, M. et al. 2021, 13. Kang, D.-W. et al. 2013, 14. Liu, S. et al. 2019, 15. Liu, Z. et al. 2021, 16. Ma, B. et al. 2019, 17. Plaza-Díaz, J. et al. 2019, 18. Pulikkan, J. et al. 2018, 19. Tomova, A. et al. 2015, 20. Wan, Y. et al. 2021, 21. Wang, L. et al. 2011, 22. Wang, M. et al. 2019, 23. Zhang, M. et al. 2018, 24. Chen, X. et al. 2013, 25. Cryan, J. F. et al. 2019, 26. Deidda, G. & Biazzo, M. 2021, 27. Dinan, T. G. & Cryan, J. F. 2017, 28. Rhee, S. H. et al. 2009, 29. Claesson, M. J. et al. 2012, 30. Salazar, N. et al. 2014, 31. Salazar, N. et al. 2017, 32. Cattell, M. et al. 2011, 33. Clarke, G. et al. 2014, 34. Diaz Heijtz, R. 2016, 35. Diaz Heijtz, R. et al. 2011, 36. Manco, M. 2012, 37. Milani, C. et al. 2017, 38. Cryan, J. F. & Dinan, T. G. 2012, 39. Houghteling, P. D. & Walker, W. A. 2015, 40. Zhuang, L. et al. 2019, 41. Clarke, G. et al. 2013, 42. Fleshner, M. et al. 2017, 43. Gomez de Agüero, M. et al. 2016, 44. O’Mahony, S. M. et al. 2017, 45. Vuong, H. E. et al. 2020, 46. Borre, Y. E. et al. 2014, 47. Gensollen, T. et al. 2016, 48. Gur, T. L. et al. 2015, 49. Dinan, T. G. & Cryan, J. F. 2017, 50. Callaghan, B. L. et al. 2020, 51. Carlson, A. L. et al. 2018, 52. Christian, L. M. et al. 2015, 53. Gao, W. et al. 2019, 54. Buie, T. et al. 2010, 55. Ferguson, B. J. et al. 2019, 56. Holingue, C. et al. 2018, 57. Johnson, C. R. et al. 2014, 58. Restrepo, B. et al. 2020, 59. Adams, J. B. et al. 2011, 60. Fouquier, J. et al. 2021, 61. Fulceri, F. et al. 2016, 62. Nikolov, R. N. et al. 2009, 63. Evans, C. et al. 2008, 64. Vuong, H. E. & Hsiao, E. Y. 2017.