Patients randomised to group A will be treated with a combination of duloxetine 60 mg per day for 29 weeks and a chronotherapeutic intervention of one weeks duration (see below). Patients randomised to group B will be treated with duloxetine in a dose of 60 mg per day for 29 weeks and individual exercise instructed by a physiotherapist. Patients will be informed that the two intervention groups are based on different time-structuring regimes. The placebo condition has been chosen to secure an similar expectancy rate in the two treatment conditions.