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Summary: 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. [ABSTRACT FROM AUTHOR]

Nightmares are often associated with psychiatric disorders and acute stress. This study explores how the COVID‐19 pandemic may have influenced the content of nightmares. A sample of N = 419 US adults completed online surveys about sleep and COVID‐19 experiences. Participants were asked about the degree to which they agreed with statements linking greater general stress, worse overall sleep and more middle‐of‐the‐night insomnia with the COVID‐19 pandemic. They were also asked if, during the pandemic, they experienced nightmares related to various themes. Logistic regression analyses examined each nightmare content as outcome and increased stress, worse sleep and more middle‐of‐the‐night insomnia as predictors, adjusted for age, sex and race/ethnicity. Those who reported greater general COVID‐related stress were more likely to have nightmares about confinement, failure, helplessness, anxiety, war, separation, totalitarianism, sickness, death, COVID and an apocalypse. Those who reported worsened sleep were more likely to have nightmares about confinement, oppression, failure, helplessness, disaster, anxiety, evil forces, war, domestic abuse, separation, totalitarianism, sickness, death, COVID and an apocalypse. Those who reported worsened middle‐of‐the‐night insomnia were more likely to have nightmares about confinement, oppression, failure, helplessness, disaster, anxiety, war, domestic abuse, separation, totalitarianism, sickness, death, COVID and an apocalypse. These results suggest that increased pandemic‐related stress may induce negatively‐toned dreams of specific themes. Future investigation might determine whether (and when) this symptom indicates an emotion regulation mechanism at play, or the failure of such a mechanism. [ABSTRACT FROM AUTHOR]

While there is an extensive literature on predisposing, precipitating, coping, and perpetuating factors in those with chronic insomnia, very little work has been undertaken to evaluate these factors over the early developmental course of insomnia. The present aim was to determine whether several hypothesized factors in each domain (predisposing, precipitating, coping, and perpetuating), assessed during an episode of acute insomnia (AI), are related to its persistence or remission to normal sleep. Participants comprised n = 140 people with AI and n = 737 normal sleepers (NS) recruited from the general public. Participants completed measures assessing predisposing characteristics (personality traits, arousal predisposition, and insomnia vulnerability), precipitating events and outcomes (life events, perceived stress, anxiety, and depression), coping styles (thought control strategies and coping styles), and perpetuating factors (sleep preoccupation, pre-sleep arousal, dysfunctional beliefs, and fatigue). Additionally, insomnia status (from AI at baseline to its persistence or natural remission [NR]) was assessed 1 month later (n = 129). Baseline differences between NS and individuals with AI were observed in each domain with increasing age, lower openness to experience and conscientiousness, higher insomnia severity, levels of anxiety, and affective sleep preoccupation significantly predicting AI status. Further, a previous episode of insomnia, higher depression scores, and affective sleep preoccupation scores significantly predicted its persistence, as opposed to its NR. Results are discussed with reference to the conceptualization of insomnia and how the findings may influence the design of preventative interventions to circumvent the transition from acute to chronic insomnia., (© Sleep Research Society 2021. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)