Long-term and even life-long drug treatment is a characteristic feature of modern psychiatric therapy. This is due to the fact that many psychiatric patients suffer from recurrent diseases for which the risk of relapses can be calculated with certain probabilities. The drugs used for treatment and prevention of these diseases are investigated insufficiently, particularly as regards their chronic effects. There exist hundreds of controlled, mainly phase III trials lasting several weeks. However, controlled long-term phase IV trials such as in the area of lithium or neuroleptic maintenance treatment are rare and have never been performed for longer than 3 years (3, 4, 9, 10).