If a person is used to a certain amount of caffeine intake daily, and they suddenly switch to decaf coffee, their body may experience headaches as their body begins to adjust to a lowered intake of caffeine. These are called caffeine withdrawal headaches. These headaches have the dilated blood vessel component that occurs with migraines (because daily caffeine had been constricting your blood vessels and now it isn't), while also carrying with it the muscle pain component of tension headaches, causing pressure to be felt around the shoulders, neck, and scalp.