Sleep-related memory consolidation in depression: an emerging field of research

The impact of sleep on eyewitness identifications

Sleep aids the consolidation of recently acquired memories. Evidence strongly indicates that sleep yields substantial improvements on recognition memory tasks relative to an equivalent period of wake. Despite the known benefits that sleep has on memory, researchers have not yet investigated the impact of sleep on eyewitness identifications. Eyewitnesses to crimes are often presented with a line-up (which is a type of recognition memory test) that contains the suspect (who is innocent or guilty) and fillers (who are known to be innocent). Sleep may enhance the ability to identify the guilty suspect and not identify the innocent suspect (i.e. discriminability). Sleep may also impact reliability (i.e. the likelihood that the identified suspect is guilty). In the current study, we manipulated the presence or the absence of sleep in a forensically relevant memory task. Participants witnessed a video of a mock crime, made an identification or rejected the line-up, and rated their confidence. Critically, some participants slept between witnessing the crime and making a line-up decision, while others remained awake. The prediction that participants in the sleep condition would have greater discriminability compared to participants in the wake condition was not supported. There were also no differences in reliability.

The influence of daytime napping versus controlled activity on the subjective well-being of patients with major depression

While the impact of sleep on cognitive functions such as memory is under extensive study, the role of sleep in modulating a persons' subjective well-being remains largely uncharacterized, especially in groups with psychiatric disorders. To gather more information on this topic a study was conducted with 20 patients suffering from Major Depression (MD) and 20 healthy controls, matched for age, gender and education. All subjects rated their subjective well-being at 10a.m. in the morning. Half of the subjects in each experimental group were given the opportunity to nap in the afternoon between 2p.m. and 3.30p.m., while the other half stayed awake accompanied by controlled activity. All subjects rated their subjective well-being again at 4p.m. Only the group of patients with MD who were given the opportunity to sleep during the day showed a significant improvement in subjective well-being from morning to afternoon. All the other subgroups showed no significant changes across the time interval. The results of this study suggest that depressive patients benefit from daytime naps with regard to their subjective well-being. Further research is needed to determine the exact mechanisms of this improvement.

Sleep and its importance in adolescence and in common adolescent somatic and psychiatric conditions

Restoring sleep is strongly associated with a better physical, cognitive, and psychological well-being. By contrast, poor or disordered sleep is related to impairment of cognitive and psychological functioning and worsened physical health. These associations are well documented not only in adults but also in children and adolescents. Importantly, adolescence is hallmarked by dramatic maturational changes in sleep and its neurobiological regulation, hormonal status, and many psychosocial and physical processes. Thus, the role of sleep in mental and physical health during adolescence and in adolescent patients is complex. However, it has so far received little attention. This review first presents contemporary views about the complex neurobiology of sleep and its functions with important implications for adolescence. Second, existing complex relationships between common adolescent somatic/organic, sleep-related, and psychiatric disorders and certain sleep alterations are discussed. It is concluded that poor or altered sleep in adolescent patients may trigger and maintain many psychiatric and physical disorders or combinations of these conditions, which presumably hinder recovery and may cross into later stages of life. Therefore, timely diagnosis and management of sleep problems appear critical for growth and development in adolescent patients.