Short video platforms such as Douyin have become deeply embedded in everyday digital life, reshaping leisure, emotion, and identity, but their immersive features also pose cognitive and psychological risks. This study examines how social presence and physical presence jointly influence two interrelated outcomes among young Chinese users: short video addiction and cognitive fatigue. Using survey data from 649 participants, we employed both PLS-SEM and fsQCA to identify linear relationships and configurational patterns. Results show that all hypothesized relationships are supported except the direct effect of emotional fatigue on cognitive fatigue. Social presence primarily increases addiction through hedonic pleasure, whereas physical presence exerts its influence through loss of control. The fsQCA findings further reveal that severe cognitive deterioration emerges not from any single factor but from dynamic combinations of emotional, cognitive, and behavioral conditions. Integrating presence and media theories, this study links algorithmic engagement to mental health risks. Given the cross-sectional design, the findings should be interpreted as associative rather than causal.