What would make someone pass out while sitting?

Someone might pass out while sitting due to a sudden drop in blood pressure, which can occur from dehydration, standing up too quickly, or prolonged sitting. Other potential causes include fainting spells triggered by stress, anxiety, or pain, as well as medical conditions like arrhythmias or low blood sugar. Additionally, certain medications or substances, such as alcohol, can contribute to loss of consciousness. It's important to seek medical attention if this occurs frequently.