Normal sleep is essential for health and wellbeing. Symptoms and signs of disturbed sleep are common in psychiatric disorders. Sleep is, by nature, adaptive to environment. Thus, short-term disturbances in sleep are frequent in population, in particular in relation to psychological or circadian stress. When more chronique, insufficient or qualitatively poor sleep increases the risk for many common diseases, such as mood disorders or Alzheimer's disease. There is large inter-individual variation in both immediate and late effects of sleep insufficiency. One of our goals is to understand the processes behind this variability. We propose that only by understanding the basic mechanisms for regulation of sleep, emotions and cognitive processes, and the inter-individual variation behind the reactivity of these mechanisms, one can develop targeted, individualized tools to ameliorate sleep- and stress-related disturbances.