The main objective of this study is to see whether the favorable preventative effect of Atorvastatin 40mg per day in episodic migraine, that was found previously in three smaller randomized controlled cross-over studies, can be confirmed in a larger, multicenter, randomized controlled parallel group study. In addition it will be investigated whether 1) the favorable side effect profile, seen in previous studies, can be confirmed, and whether it is even better with the smaller dose, and 2) estimating the cost of Atorvastatin treatment, considering cost of medicine, cost of acute attack medicine, and cost of lost worktime.

Inclusion Criteria:

1. Age 18 to 64 years
2. Signed informed consent
3. Chronic migraine according to ICHD-3 criteria (32)
4. At inclusion, patients should retrospectively have at least 15 headache days per month wheof at least 8 migraine days during the last 3 months. This frequency must be confirmed in the headache diary before randomisation to treatment (See below).
5. Debut of migraine at least one year prior to inclusion based on information in the patient record or by careful examination of previous headache history
6. Start of migraine before age 50 years.
7. No use of other migraine prophylactics during the study
8. For women of child-bearing potential (WOCBP, see below) there must be no pregnancy or planned pregnancy during the study period, and use of highly effective contraception (See below).

After the baseline period, just before randomisation to the study drug, inclusion criteria will be evaluated once more, and the headache diary will be evaluated. If there are, according to the headache diary, fewer migraine days than 8 per month, the baseline period can be extended to 8 weeks.

Exclusion Criteria:

1. Medication overuse headache requiring detoxification from acute medication (triptans, opioids). Exception could be made for those fulfilling A and B:

   A. Have tried a withdrawal period of at least 2 months without impact on headache frequency B: Use of opioids (of any type) ≤ 8 days /months.

2. Pregnancy, planning to get pregnant, inability to use contraceptives (See inclusion criteria, point 8), and lactating

3. Clinical information on or signs of cholestasis or decreased hepatic or renal function.

4. High degree of comorbidity and/or frailty associated with reduced life expectancy or high likelihood of hospitalization, at the discretion of the investigator

5. Hypersensitivity to statins or previous use of statins

6. History of angioneurotic oedema

7. Use of medicines for migraine prophylaxis less than 4 weeks, or of botulinum toxin less than 16 weeks, prior to start of study

8. Current use of antiviral treatment agaist hepatitis C

9. Significant psychiatric illness

10. Alcohol or illicit drug dependence.

11. Inability to understand study procedures and to comply with them for the entire length of the study

12. Treatment for hypothyroidism

13. Lactose intolerance

Triple blind (blinded to patients, study personnel, and statistician)