Tension headache: This is the most common type of headache and is often described as a band or a squeezing sensation around the forehead, usually bilateral but can be unilateral, and can worsen with activities that increase intracranial pressure such as bending over or sneezing.

Migraine: Although migraines are typically unilateral and can be accompanied by other symptoms such as nausea, vomiting, and sensitivity to light and sound, some individuals may experience migraines that worsen with physical activity or changes in intrathoracic pressure.
Temporal arteritis (Giant Cell Arteritis): This condition, more common in older adults, involves inflammation of the blood vessels and can cause headaches, typically unilateral and temporal, which may worsen with activities that increase intracranial pressure. However, it's less likely than tension headache but should be considered due to its potential for serious complications.
Sinusitis: Inflammation of the sinuses can cause headaches, often described as worsening with bending over or straining, due to increased pressure in the sinuses.

Subarachnoid hemorrhage: Although less common, a sudden, severe headache that worsens with activities such as sneezing or bending over could be indicative of a subarachnoid hemorrhage, which is a medical emergency.
Brain tumor: A headache that worsens with activities that increase intracranial pressure could be a sign of a brain tumor, especially if accompanied by other neurological symptoms.
Idiopathic intracranial hypertension (IIH): Characterized by increased intracranial pressure without a detectable cause, IIH can cause headaches that worsen with activities that further increase intracranial pressure.

Trigeminal neuralgia: While this condition typically causes sudden, severe, shock-like pain around the eyes, nose, or jaw, it could potentially cause temporal headaches that worsen with specific triggers.
Arteriovenous malformation (AVM): A rare condition where there's an abnormal connection between arteries and veins in the brain, which could potentially cause headaches that worsen with increased intracranial pressure.
Chiari malformation: A structural defect in the cerebellum that controls balance, can cause headaches that worsen with coughing, sneezing, or straining, due to increased pressure on the brain and spinal cord.