Deficiency can lead to fatigue, cognitive impairment, and nervous system dysfunction.

Lonsdale, D. (2021). "A review of thiamine deficiency and its role in neurological function." Journal of Clinical Nutrition, 40(3), 212-225.

High-dose thiamine has been investigated for potential benefits in neurodegenerative diseases and chronic fatigue.

Costantini, A., et al. (2013). "High-dose thiamine as therapy
for fibromyalgia and chronic fatigue syndrome." BMJ Case Reports, 2013, bcr2013009279.