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 mild to moderate in severity. It's frequently associated with stress, fatigue, or poor posture, making it a likely diagnosis in a young adult.

Migraine: Although less common than tension headaches, migraines can occur in young adults and are characterized by severe, throbbing pain, often unilateral, and can be accompanied by nausea, vomiting, and sensitivity to light or sound.
Sinus headache: Headaches caused by sinusitis or sinus infections can be a consideration, especially if the patient has symptoms of a cold, fever, or facial pain.
Cluster headache: These are severe, one-sided headaches that occur in clusters or cycles, but they are less common and typically start at an older age.

Subarachnoid hemorrhage: A life-threatening condition caused by bleeding into the space surrounding the brain, often presenting with a sudden, severe headache (often described as "the worst headache of my life"), which requires immediate medical attention.
Meningitis: Inflammation of the protective membranes covering the brain and spinal cord, which can present with headache, fever, stiff neck, and confusion, and is a medical emergency.
Brain tumor: Although rare, a brain tumor can cause headaches, especially if they are worsening over time, occur at the same time every day, or are accompanied by other neurological symptoms like seizures or weakness.

Temporal arteritis: An inflammation of the blood vessels in the head, more common in older adults, but can occur in younger individuals, presenting with headache, jaw claudication, and visual disturbances.
Idiopathic intracranial hypertension (IIH): A condition characterized by increased pressure within the skull without a detectable cause, often presenting with headache, vision changes, and tinnitus, more common in obese young women but can occur in anyone.
Trigeminal neuralgia: A chronic pain condition that affects the trigeminal nerve, which carries sensation from your face to your brain, causing intense, shock-like or stabbing pain in parts of your face.