Maternal depressive symptoms and mother-infant co-sleeping (including room sharing and bedsharing): a systematic review.

STUDY OBJECTIVES: Maternal depressive symptoms (MDS) affect most women during the first year postpartum. Mothers provide most of the nighttime care for infants, so studying the relationship between MDS and infant sleep location (ISL) is highly relevant to understanding maternal mental health over the first year of life and beyond. Infant sleep is studied by anthropologists, health care providers, and psychologists, with very little communication across disciplines. This review aimed to determine if there is a predictive relationship between MDS and ISL. METHODS: This systematic review searched six databases with terms related to maternal mood and ISL. Final analysis included 14 published studies, analyzed with narrative synthesis and PRISMA guidelines. Included studies directly compared infant sleep location (ISL) and maternal depressive symptoms (MDS). RESULTS: Five studies showed no relationship between ISL and MDS, and one study found bedsharing reduced MDS. Five studies found co-sleeping was related to higher MDS although directionality is mixed or missing, and three studies found an association at some ages or for some populations only. Examining studies according to type of infant sleep assessment, study design, age of infant, or breastfeeding status failed to detect consistent patterns. CONCLUSIONS: A variety of study designs, types and definitions of variable measures, sample recruitment and study outcomes prevent detection of a consistent relationship between MDS and ISL. We explore reasons for the elusive nature of a relationship and make recommendations for future research in MDS and ISL, including cross-disciplinary collaborations.

Using complexity science to understand the role of co-sleeping (bedsharing) in mother-infant co-regulatory processes.

Human infants spend most of their time sleeping, but over the first few years of life their sleep becomes regulated to coincide more closely with adult sleep (Galland et al., 2012; Paavonen et al., 2020). Evidence shows that co-sleeping played a role in the evolution of infant sleep regulation, as it is part of an ancient behavioral complex representing the biopsychosocial microenvironment in which human infants co-evolved with their mothers through millions of years of human history (Ball, 2003; McKenna 1986, 1990). This paper is a conceptual, interdisciplinary, integration of the literature on mother-infant co-sleeping and other mother-infant co-regulatory processes from an evolutionary (biological) perspective, using complexity science. Viewing the mother-infant dyad as a "complex adaptive system" (CAS) shows how the CAS fits assumptions of regulatory processes and reveals the role of the CAS in the ontogeny of mother-infant co-regulation of physiological (thermoregulation, breathing, circadian rhythm coordination, nighttime synchrony, and heart rate variability) and socioemotional (attachment and cortisol activity) development.

Reasons mothers bedshare: A review of its effects on infant behavior and development.

Bedsharing is controversial for nighttime caregiving in the U.S. today, as in most of the West. However, from the standpoint of evolutionary pediatrics, anthropology, and cultural psychology, bedsharing is not controversial at all, representing the context for human infant evolution and conferring a host of physiological benefits to the infant as well as the mother. In an effort to understand the rise in Western bedsharing in recent decades (and following Ball, 2002; McKenna & Volpe, 2007), Salm Ward (2015) systematically reviewed the literature on mother-infant bedsharing and identified ten reasons why mothers choose to bedshare: (1) breastfeeding, (2) comforting for mother or infant, (3) better/more sleep for infant or parent, (4) monitoring, (5) bonding/ attachment, (6) environmental reasons, (7) crying, (8) cultural or familial traditions, (9) disagree with danger, and (10) maternal instinct. The current paper offers the "review behind the review," highlighting the scientific evidence behind the reasons mothers give for their decision to bedshare, focusing on how mothers' decisions about infant sleep location influence infant behavior and development.

Sleep Consolidation, Sleep Problems, and Co-Sleeping: Rethinking Normal Infant Sleep as Species-Typical.

Infants evolved in the context of close contact (including co-sleeping). Evolutionary context is rarely considered in psychological infant sleep research, and Western sleep researchers make assumptions about what optimal "normal" infant sleep is and how to achieve early, deep, infant sleep consolidation and avoid infant sleep problems. However, an evolutionary and anthropological view of infant sleep as species-typical recognizes that human evolution likely prepared the infant brain for optimal development within its evolutionary context - co-sleeping. Thus, "normal" infant sleep, sleep consolidation, and sleep problems should all be understood within the framework of co-sleeping infants, not the historically new-phenomenon of solitary-sleeping infants. Much work needs to be done in order to understand "normal" infant sleep as species-typical and how adaptive infants are to environments that stray from their evolutionary norm.

What Is "Normal" Infant Sleep? Why We Still Do Not Know.

The human need for sleep is universal and unquestioned; however, humans vary in their sleep needs according to age, individual differences, as well as cultural and social norms and practices. Therefore, what is "normal" in infant sleep and the development of sleep architecture in humans is highly dependent on biological and sociocultural variables as well as socially constructed assumptions about what infant sleep "should" look like. This paper uses a multidisciplinary approach to review papers from fields including pediatrics, anthropology, psychology, medicine, and sociology to understand "normal" infant sleep. Because human culture and behavioral practice changes much more quickly than evolved human biology, and because human evolutionary history occurred in the context of breastfeeding and cosleeping, new work in the field of infant sleep architecture development would benefit from a multidisciplinary approach. To come to a consensus about what is "normal" infant sleep, researchers must agree on underlying basic assumptions of infant sleep from which to ask question and interpret findings.

Co-sleeping as a proximal context for infant development: The importance of physical touch.

Co-sleeping is a complex familial phenomenon that has yet to be well understood by Western scientists. This paper provides an interdisciplinary review of research from anthropology, nursing, pediatrics, sociology, social work, public health, family studies, and psychology to focus on the role of physical touch in the context of co-sleeping, and how close physical contact in this context affects infants and their caregivers. Including an anthropological, evolutionary view of co-sleeping with other perspectives highlights it as an experience-expectant proximal context for infant growth and development. From this view, the importance of physical contact and touch in the nighttime caretaking microenvironment of co-sleeping becomes a central question, rather than an artifactual byproduct of "unhealthy" sleep arrangements. Rather than trying to eliminate co-sleeping, public health messages for parents would likely benefit from a more culturally-sensitive approach that focuses on advising how to co-sleep safely for families choosing it. For families trying to retain physical closeness between parent(s) and infants in the context of modern (especially Western) infant care practices that have reduced this physical contact, co-sleeping can be an important developmental context for encouraging and engaging in sensitive and responsive caregiving and providing a context for maternal-infant physiological synchrony and regulation.

Does conceptual implicit memory develop? The role of processing demands.

The author investigated the importance of processing considerations within implicit memory in a developmental design. Second-graders (n = 87) and college students (n = 81) completed perceptual (word stem completion) and conceptual (category generation) implicit memory tests after studying target items either nonsemantically (read) or semantically (generated). In support of previous research, the author found no age differences in priming in the nonsemantic study/perceptual test condition. Age differences in priming were found in the semantic study/conceptual test condition, however, where college students had significantly higher priming scores than did children. These developmental dissociations support the theory that the processing requirements of conceptual implicit memory are similar to those in explicit memory. The author also discusses the contribution of the Transfer Appropriate Processing (TAP; H. L. Roediger, D. A. Gallo, & L. Geraci, 2002) framework to understanding these findings.

Depression, implicit memory, and self: a revised memory model of emotion.

Cognitive constructs are explored for clinical psychologists interested in cognitive phenomena in depression. Both traditional and modern memory constructs are outlined and described with attention to their contribution to understanding depression. In particular, the notions of memory construction, self-schemas, and autobiographical memory (per [Conway, M.A. (2001). Sensory-perceptual episodic memory and its context: Autobiographical memory. Philosophical Transactions of the Royal Society of London: Biological Sciences, 356, 1375-1384.]) are discussed. Then, the phenomenon of implicit memory is described as a way to bring these constructs together to understand depression. The Rehm and Naus (1990) [Rehm, L.P., and Naus, M.J. (1990). A memory model of emotion. In Ingram, R.E. (Ed.), Contemporary Psychological Approaches to Depression (pp. 23-35). New York: Plenum Press.] memory model of emotion is updated and expanded to include these cognitive constructs, and depression is viewed from the perspective of understanding interactions between explicit and implicit memory processes.