The investigators aim is to evaluate effects of combined oral contraceptives (OC) on mood, sexuality and economic behaviour in a randomized, double-blind, placebo-controlled study. 400 healthy women will be randomized to OC or placebo for a period of three months. Before and at the end of treatment, mood and sexuality will be assessed by validated instruments. At the end of treatment, each woman will participate in behavioral experiments testing self-confidence, risk taking and altruism. The current project could fill the gap of ignorance about causal effects of OCs on mood, sexuality and behavior. The results might improve current practice as regards information about OCs, choice of hormonal contraceptive, regimen and duration of use. As a consequence, this could lead to reduced discontinuation rate, fewer unintended pregnancies and abortions. The project will contribute to an overall improvement in women's reproductive health.