Environmental restraint: A hidden risk factor for stress-induced depression in rats.

Little is known about the impact of environmental restraint, characterized by limited space and a lack of stimulating elements, on adult mental and physical health. We examined the influence of environmental restraint on depression-like behaviors and physical status in rats, and the potential mitigating effects of Lactococcus cremoris H61 as a beneficial bacterium. Rats subjected to environmental restraint exhibited prolonged maladaptive immobility in the forced swim test without showing changes in body weight, locomotion, or social motivation. Daily activities remained unaffected. These findings suggest that environmental restraint may be a covert risk factor for stress-induced depression, potentially alleviated by supplementation with strain H61.