Vasovagal Syncope: This is the most common cause of syncope, especially in young adults, often triggered by stress, pain, or prolonged standing, resulting in a sudden drop in blood pressure and heart rate.

Orthostatic Hypotension: A drop in blood pressure upon standing, common in the elderly, those with dehydration, or on certain medications, leading to reduced blood flow to the brain.
Cardiac Arrhythmias: Conditions like atrial fibrillation or ventricular tachycardia can lead to syncope by disrupting the normal heart rhythm, thereby reducing cardiac output.
Hypertrophic Cardiomyopathy: A heart condition where the heart muscle becomes thickened, which can obstruct blood flow and lead to syncope, especially during exertion.

Pulmonary Embolism: Although less common, a pulmonary embolism can cause syncope due to a sudden blockage of a pulmonary artery, which is life-threatening and requires immediate medical attention.
Aortic Dissection: A tear in the aorta's inner layer can lead to syncope among other symptoms, and is a medical emergency due to the risk of aortic rupture.
Cardiac Tamponade: Fluid accumulation in the sac around the heart can compress the heart, reducing its ability to pump blood effectively, leading to syncope and potentially death if not promptly treated.

Subclavian Steal Syndrome: A rare condition where there's a reversal of blood flow in the subclavian artery, which can lead to syncope due to decreased blood flow to the brain.
Micturition Syncope: Syncope triggered by urination, often due to a sudden drop in blood pressure, more common in older men.
Defecation Syncope: Similar to micturition syncope but triggered by defecation, also resulting from a sudden drop in blood pressure.
Carotid Sinus Syncope: A rare form of syncope caused by an exaggerated response to carotid sinus baroreceptor stimulation, often triggered by neck movements or tight collars.