The relationships between insomnia, nightmares, and dreams: A systematic review.

Insomnia and nightmares are both prevalent and debilitating sleep difficulties. The present systematic review aims to document the relationships between insomnia and nightmares in individuals without a concomitant psychopathology. The relationships between insomnia and dreams are also addressed. PsycINFO and Medline were searched for papers published in English or French from 1970 to March 2023. Sixty-seven articles were included for review. Most results support positive relationships between insomnia variables and nightmare variables in individuals with insomnia, individuals with nightmares, the general population, students, children and older adults, and military personnel and veterans. These positive relationships were also apparent in the context of the COVID-19 pandemic. Some psychological interventions, such as Imagery Rehearsal Therapy, might be effective in alleviating both nightmares and insomnia symptoms. Regarding the relationships between insomnia and dreams, compared with controls, the dreams of individuals with insomnia are characterized by more negative contents and affects. The results show that insomnia and nightmares are connected and may be mutually aggravating. A model is proposed to explain how insomnia might increase the likelihood of experiencing nightmares, and how nightmares can in turn lead to sleep loss and nonrestorative sleep.

The effectiveness of stimulus control in cognitive behavioural therapy for insomnia in adults: A systematic review and network meta-analysis.

Stimulus control is part of the widely used cognitive behavioural therapy for insomnia. However, there is a lack of knowledge about its mechanisms of action and effectiveness when used alone. This systematic review with network meta-analysis aimed to evaluate stimulus control efficacy when used alone compared with cognitive behavioural therapy for insomnia or its components. The review also documented stimulus control mechanisms of action proposed by the authors. A search was conducted in several bibliographic databases (MEDLINE, PsycINFO, Embase, CINAHL, Psychology Behavioural Sciences Collection, Web of Science, and Cochrane Library) and in two registers from 1972 to June 2022. Randomised studies with adult participants presenting a diagnosis of insomnia and including at least one stimulus control instruction in a treatment group were included. Risk of bias was assessed with the Quality Assessment of Controlled Intervention Studies. Twenty-three studies were included and three network meta-analyses were conducted. The quality of included studies was generally poor. Results indicate that stimulus control is an effective intervention to improve insomnia compared with control conditions. Not all stimulus control instructions seem essential, especially those known to recondition the bedroom for sleep. The review challenges the classical conditioning hypothesis. Results should be interpreted cautiously given the small number of studies included, bias risk, and inconsistencies in the network meta-analysis. Rigorous research is needed in evaluating stimulus control efficacy and mechanisms.

Sleep in times of crises: A scoping review in the early days of the COVID-19 crisis.

During the early days of the pandemic and in the context of a seemingly unknown global threat, several potential major sleep disruptors were identified by sleep researchers and practitioners across the globe. The COVID-19 pandemic combined several features that, individually, had been shown to negatively affect sleep health in the general population. Those features included state of crisis, restrictions on in-person social interactions, as well as financial adversity. To address the lack of a comprehensive summary of sleep research across these three distinctive domains, we undertook three parallel systematic reviews based on the following themes: 1) Sleep in times of crises; 2) Sleep and social isolation; and 3) Sleep and economic uncertainty. Using a scoping review framework, we systematically identified and summarized findings from these three separated bodies of works. Potential moderating factors such as age, sex, ethnicity, socioeconomic status, psychological predisposition, occupation and other personal circumstances are also discussed. To conclude, we propose novel lines of research necessary to alleviate the short- and long-term impacts of the COVID-19 crises and highlight the need to prepare the deployment of sleep solutions in future crises.