What causes headaches and when should you worry?

Headaches are most commonly caused by tension, stress, dehydration, poor sleep, eye strain, or skipping meals. Migraines involve neurological changes that cause throbbing pain, often with light sensitivity or nausea. Sinus congestion, caffeine withdrawal, and muscle tightness in the neck and shoulders are also frequent culprits. You should seek immediate medical attention if a headache comes on suddenly and severely like a thunderclap, as this can signal a brain aneurysm. Also see a doctor if headaches are accompanied by fever, stiff neck, confusion, vision changes, weakness, or follow a head injury. Headaches that are progressively worsening, waking you from sleep, or changing in character over time also warrant evaluation to rule out serious underlying conditions.