Certain chemicals in the brain (e.g. dopamine and serotonin) may be responsible for the onset of migraines. These chemicals are called neurotransmitters because they spread signals in the brain. Neurotransmitters can cause blood vessels to act in unusual ways if they are present in irregular amounts or if the blood vessels are mainly sensitive to them. Different people typically have different triggers, such as certain foods, stress or tension or even birth control pills. Medical Cannabis was a standard treatment for migraines from the mid-19th century until it was outlawed in the early 20th century in the USA. It has been reported to help people through an attack by relieving the nausea and dulling the head pain, as well as possible preventing the headache completely when used as soon as possible after the onset of pre-migraine symptoms, such as aura. There is some indication that semi-regular use may reduce the frequency of attacks.
