Myotonic dystrophy type I (DM1) is one of the most variable of all human disorders, with virtually all body systems affected in some way, and age at disease onset varies from fetal life to old age. The character of DM1-related excessive daytime sleepiness (EDS) is that of a persistent sleepiness unaffected by naps, the latter being long, unrefreshing and without any associated dream. This chapter presents the scores of DM1 patients with and without EDS on the eight Short-Form 36-item Health Survey subscales, a frequently used generic health-related quality of life (HRQoL) questionnaire. It describes the personality and cognitive characteristics of 200 DM1 patients with and without EDS. The chapter discusses the habitual sleep-wake schedule and sleep-related complaints of 200 DM1 patients with and without EDS. Sleep-disordered breathing (SDB), hypercapnia, and nocturnal desaturation are all frequent in DM1. Psychostimulant drugs are increasingly used to treat EDS in DM1.

This chapter briefly discusses the genetic underpinnings, physical features and natural history of Williams syndrome and Smith-Magenis syndrome, and the cognitive and behavioural characteristics associated with these conditions in childhood. It then explores their long-term course, their effects on adjustment in adulthood and implications for support and intervention for affected individuals across the life span. Williams syndrome is a developmental disorder involving the vascular, connective tissue and central nervous systems. Studies have highlighted a distinctive psychological profile, and unusual personality and behavioural characteristics that are associated with Williams syndrome that differentiate affected children from other groups with learning disabilities. Children with Smith-Magenis syndrome tend to pose severe management problems for their carers due to hyperactivity, aggressive outbursts, self-injurious behaviours and sleep disturbance. Parents' interventions have focused on keeping their children safe at night and attempting to minimize the sleep disruption caused by night-waking.