Sarah E. Johns

Perceived environmental risk as a predictor of teenage motherhood in a British population

Previous studies have shown that strong relationships exist between deprived environments and teenage motherhood. However, such studies have predominantly identified deprivation using neighbourhood-wide measures of socio-economic status. Few studies of teenage parenthood have examined how individuals perceive their environment and the importance of this perception on reproductive behaviour and timing. Using data collected from a sample of women living the county of Gloucestershire, UK, this paper explores the predictive value of two methods of assessing the environment: (1) the structural component-deprivation at the neighbourhood level and (2) the individuals subjective experience of her pre-pregnancy environment, when examining how the wider environmental context can influence the decision of becoming a teenage mother. The results indicate that a womans perception of her neighbourhood of residence at the time she conceived, her perceived environmental risk, may be a more discriminating predictor of teenage motherhood than deprivation measured by ward economic and deprivation indicators.

Teenage pregnancy and motherhood: How might evolutionary theory inform policy?

Abstract Teenage pregnancy and motherhood are considered to be pressing social concerns and, in the majority of developed countries, are often viewed as problems in need of solutions. While a number of factors are associated with teenage motherhood, the underlying causes remain elusive. Despite a lack of consensus, policy aimed at ‘solving’ teenage motherhood is typically based on these proposed proximate correlates; addressing these, rather than the cause. Recent appraisals of this approach suggest that it may not be working effectively, if at all, and policy makers might be in need of some novel approaches. This paper discusses how policy decisions concerning reproductive timing may benefit from the perspective provided by evolutionary life-history theory, and why policy ought to take into account the hypothesis that teenage motherhood is the outcome of an adaptive response of an evolved reproductive strategy to conditions of risk and uncertainty; that having children at an earlier age may promote linea...

Subjective life expectancy predicts offspring sex in a contemporary British population

There is evidence that women who are in poor physical condition or who reside in deprived environments are more likely to give birth to daughters than to sons. Under deprived environmental conditions, or when in poor physical health, it has been hypothesized that parents should take into account the available resources and manipulate the sex of any children born. Using subjective life expectancy (SLE) as a measure of how an individual views their future health and environment, I demonstrate that there is an association between the sex of the first child and SLE in a sample of mothers from a contemporary British population (Gloucestershire, UK). SLE was a significant predictor of offspring sex: women who believed that they had longer to live were more likely to have had a male birth than women who thought they would die earlier. Detection of such a bias among the children of British mothers may provide evidence that the sex ratio under relatively affluent Western conditions can still be influenced by adverse environmental or poor maternal condition.

Postnatal depression and reproductive success in modern, low-fertility contexts

Postnatal depression reduces completed fertility; women who experience it early in their childbearing careers are less likely to have a third birth. Postnatal depression at the first birth leads to lowered fertility levels, indicating a causal role in population ageing and highlighting a new incentive to invest in prevention.

Male infants and birth complications are associated with increased incidence of postnatal depression

RATIONALE A growing body of literature links both depressive symptoms generally, and those specifically in the postnatal period, with an inflammatory immune response. Evolutionary medical approaches, such as the Pathogen Host Defence Theory of Depression (PATHOS-D), have likened depression to sickness behaviour in other mammals, and propose that the characteristics associated with depression are protective when an individual is experiencing pathogenic threat. Many known risk factors for depressive symptoms are associated with activation of inflammatory pathways, opening up the potential for identifying novel risk factors based on their inflammation causing effects. OBJECTIVE Both the gestation of male foetuses and the experience of birth complications have documented associations with increased inflammation, yet their relationships with postnatal depression (PND) are currently unclear. METHOD Here we use the complete reproductive histories of 296 women from contemporary, low fertility populations gathered by retrospective survey to assess whether the odds of PND increased when mothers gave birth to male infants or experienced birth complications, using generalised estimating equation models controlling for individual effects of the mother and other known PND risk factors. RESULTS We found the odds of PND increased by 71-79% when male infants were born compared to female infants. The occurrence of birth complications increased the odds of PND by 174% compared to having no complications. Testing for interaction effects found that, while always at increased risk of PND, women with a tendency towards symptoms of depression, anxiety, and stress at other points in the life course had reduced odds of PND when experiencing birth complications, suggesting such women may elicit greater support. CONCLUSIONS These results highlight two novel PND risk factors, male infants and birth complications, which can be easily assessed by health professionals.

Postnatal depression is associated with detrimental life-long and multi-generational impacts on relationship quality

Postnatal depression (PND) is known to be associated with a range of detrimental child and adolescent outcomes, resulting from its disruptive impact on mother-child relationship quality. However, until now little has been known about the impact of PND on the longer-term relationships between mothers and their children, and any intergenerational effects this may have. Mother-child relationship quality is of interest from an evolutionary perspective as it plays a role in the accrual of offspring embodied capital, thus affecting offspring quality and offspring’s capacity to subsequently invest in their own children. Relationships with offspring also mediate grandparent-grandchild relations; if PND negatively affects long-term mother–offspring relationship quality, it is also likely to negatively affect grandmaternal investment via reduced grandmother–grandchild relationship quality. Here, we use responses to a retrospective questionnaire study of postmenopausal women, largely from the UK and US, to assess the impact of PND occurring in generation 1 on mother–child relationship quality across the life course of the child (generation 2) with whom it was associated, and also on the relationship quality with grandchildren (generation 3) from that child. Average mother-child relationship quality was lower when the child’s birth was associated with PND. Multi-level regression modelling found that mother-child relationship quality decreased as PND symptom severity increased after controlling for individual effects and a variety of other factors known to influence relationship quality (individual mothers n = 296, mother-child dyads n = 646). Additionally, intergenerational relationships appear to be affected, with PND negatively associated with grandmother-grandchild relations (individual grandmothers n = 125, relations with grandchildren from n = 197 grandmother-parent dyads). That PND has long-term detrimental consequences for mother-child relationships, well beyond adolescence, highlights the need for investment in strategies to prevent PND and its cascade of negative multigenerational effects.

Reply to Hagen and Thornhill

We thank Hagen and Thornhill for their thoughtful comments on our paper [1]. We appreciate, based on the explanation provided in their commentary, that model we tested differed somewhat from their psychic pain hypothesis (PPH). Furthermore, we are pleased that our article has sparked debate and has afforded them the opportunity to further clarify their ideas for the purposes of future analysis. It is important that evolutionary hypotheses are testable and that empirical evidence is brought to bear on them, particularly when they have the potential to positively influence public health as evolutionary approaches to mental health do. For instance, at a time when population ageing is a major source of financial strain in many industrialized societies and governments are seeking to encourage higher fertility [2], our findings highlight a potential new source of financial incentive to invest in postnatal depression (PND) screening and preventative measures. It is important to clarify when designing our study we did not have the authors work explicitly in mind. Rather, our starting point was the medical literature documenting the costly nature of experiencing depression. Our primary interest was in understanding these costs from a life history perspective. From this starting point we set out to explore what impact PND had on fertility and parity progression, following a call from demographers to address this gap in the literature [3]. Our research is the first to specifically investigate the consequences on PND on female reproductive decision making, adding to a growing literature on the importance of maternal wellbeing for female parity progression [4], irrespective of how the findings fit within a general evolutionary framework or specifically within that of the PPH. The maternal circumstances variable which Hagen and Thornhill critique was created in response to reviewers’ feedback on our original work requesting moderation analysis to explore whether the detrimental impacts of PND on parity progression held across women of differing circumstances (which we found that they did). The measure is a composite of other measures which were collected for the purpose of controlling for factors known to influence fertility, rather than specifically as measures of maternal condition, and we readily admit this is not a ‘perfect’ measure (if such a thing exists). Future work should seek to improve upon this, perhaps by collecting data on more robust markers of socioeconomic status, health markers, partner relationship dynamics and extrinsic mortality risk. Hagen and Thornhill propose a number of ways in which researchers may test their PPH in the future, which can only be welcomed. In their commentary, the authors make the uncontentious points that (i) signalling mechanisms may evolve to over-fire and (ii) various factors indicating maternal condition, and influencing both PND risk and fertility, are highly correlated between parity levels. Thus, it may not be surprising, as our results indicate, that women in positive circumstances sometimes have PND, and that repeat bouts of PND are correlated with reduced commentary 24