Beyond the Gut: A Case Report of Antibiotic-Induced Dysbiosis as a Hidden Cause of Chronic Insomnia.

Insomnia is a common sleep disorder that affects many adults on a long-term or intermittent basis. While conventional management includes pharmacotherapy and cognitive behavioral therapy, emerging evidence highlights the gut microbiome as a critical regulator of sleep via the microbiome-gut-brain axis. Prolonged antibiotic exposure can lead to an alteration or imbalance in the structure, composition, and function of the gut microbial community, known as gut dysbiosis. Gut dysbiosis may disrupt neurotransmitter synthesis and circadian rhythm, contributing to refractory insomnia. We report a 40-year-old man with early T-cell precursor acute lymphoblastic leukemia who underwent induction chemotherapy and allogeneic stem cell transplantation. Over two years, he received multiple prolonged antibiotic courses for infectious complications, resulting in significant cumulative exposure. Several months later, he developed severe insomnia, unresponsive to melatonin, mirtazapine, CBT-I, and multiple hypnotics, including zolpidem and lemborexant. Actigraphy revealed sleep latency of 90 minutes, total sleep time <4 hours, and sleep efficiency of 50-55%. Integrative evaluation demonstrated marked gut dysbiosis (low Firmicutes/Bacteroidetes ratio, overgrowth of Streptococcus, Klebsiella, Fusobacterium) and multiple micronutrient deficiencies. Targeted interventions, multistrain probiotics, fermented foods, high-fiber diet, and amino acid/vitamin supplementation, led to progressive improvement. At six months, the patient achieved restorative sleep without pharmacologic support, alongside improved mood, appetite, and functional status. This case underscores the potential role of antibiotic-induced dysbiosis in chronic insomnia through disruption of microbial metabolites (short-chain fatty acids) and neurotransmitter pathways. Restoration of gut health may modulate circadian rhythm and sleep architecture, offering a novel adjunctive strategy for refractory insomnia. Clinicians should consider gut microbiome assessment in persistent insomnia, particularly in patients with extensive antibiotic exposure. Further research is warranted to elucidate mechanisms and validate microbiome-targeted therapies.