Currently, adalimumab is given every 2 weeks, by injection under the skin. The optimal time between two injections has never been investigated before. Prior research in patients with rheumatoid arthritis shows that disease remission can be maintained with longer injection-intervals. Our hypothesis is that this is the same for Crohn's disease patients. Our aim is to show non-inferiority of extending the adalimumab dosing interval, under strict disease monitoring in Crohn's disease patients in sustained (>12 months) clinical remission, compared to standard care.