Maternal Depression: A Catalyst for Cooperation?

Image: woman in Uganda

– by Alessandra Cassar

Women around the world experience maternal depression, particularly around the time of pregnancy and childbirth. With around 10-15% of mothers in high-income countries and up to 25% in low- and middle-income countries experiencing depression during or after pregnancy, it is essential that we understand its causes and effects. But from an evolutionary perspective, why would such a costly condition even exist, if it affects not only the mother and her infant but potentially the entire family?

Patricia Schneider, Chukwuemeka Ugwu, and I decided to explore one specific theory rooted in evolutionary psychology: that maternal depression may not be solely a dysfunction but an evolved mechanism. We tested whether maternal depression could act as an unconscious bargaining strategy for mothers who had exhausted all other strategies to elicit help and support from their social network, particularly the baby’s father. This idea is controversial but offers a potential explanation for why a condition so detrimental could have persisted over evolutionary time.

Evolutionary Perspectives on Depression. Several evolutionary hypotheses suggest that depression might have evolved as an adaptive response. Depression could enable individuals to obtain help from others, encourage cognitive changes to solve social problems, or prevent individuals from engaging in risky behaviors. In other words, while depression is painful, it might serve important functions, especially when faced with adverse social situations. This idea gains more traction when we look at maternal depression, where a mother’s wellbeing directly impacts her offspring’s chances of survival.

Perinatal depression, occurring during pregnancy or shortly after birth, presents a particular challenge. Symptoms like sadness, fatigue, and loss of interest in usual activities make it hard for mothers to care for their infants. This has led some researchers to propose that maternal depression might serve as a signal—a costly, honest cry for help—that triggers increased investment from others, particularly those closest to the mother (and genetically closest to the infant).

The Bargaining Model Hypothesis. The bargaining model of maternal depression advanced by Edward Hagen proposes that depression acts as an unconscious strategy for a mother to elicit support. In evolutionary terms, a mother who experiences adversity—such as a lack of support from the baby’s father or social group—could “bargain” for more help by stopping activities that are beneficial to the baby and even to herself. This behavior, costly to everyone, herself included, would signal, through her visible depressive symptoms, that she cannot continue to care for the baby on her own and she truly needs help. This could encourage the father or others to step in and provide the necessary assistance, ensuring the survival of the offspring.

Our Work. To test this hypothesis, we conducted a study in Uganda, involving nearly 300 women around the time of giving birth. Our focus was on whether women showing signs of depression received more cooperation from their social network—specifically, their spouse, kin, and other close individuals—compared to those who did not display such symptoms. In our work, we propose to use a quasi-experimental method called regression discontinuity design (RDD), an empirical method to estimate the potentially positive causal effect of perinatal depression on cooperation within a mother’s social group, despite an expected negative relationship between the two. The negative relationship between social support and maternal well-being is bi-directional: lack of support can cause depression, while depression may reduce support as individuals tend to isolate themselves. This well-known relationship can be seen in the downward sloping predicted lines in Figure 1. However, the bargaining hypothesis suggests that depressive symptoms may also increase cooperation from others, adding a positive effect from depression to support. But how could we test for that since one cannot randomize who is depressed and who is not? Our proposed method is based on the assumption that around the threshold for depression advised by psychiatrists, being a few points below or a few points above is almost random. In this case, we could estimate whether there is a positive “jump” in support between the women right below and those right above such threshold.

Key Findings. Our findings provide some evidence in favor of the bargaining hypothesis. Comparing women just below and just above the threshold for potential depression, we observed that mothers who were at the threshold of displaying depressive symptoms did indeed receive more help, particularly from their spouse (see the positive jump/discontinuity at the threshold in the graphs of Figure 1), maternal grandparents, and a few other close kin. These results suggest that, at least in some cases, maternal depression might trigger increased cooperation from key individuals in a mother’s network.

Interestingly, non-kin such as neighbors and friends, while generally supportive, did not seem to react as strongly to a mother’s depressive symptoms. This aligns with the idea that depression’s signaling function might be more effective among genetic relatives, whose fitness is directly tied to the survival of the child.

Figure caption: Discontinuity plot: Spouse. Each graph represents the predicted line resulting from a linear regression of the corresponding support type on the depression index with a structural break at 0 (equivalent to EPDS=10), and a 95% confidence interval. The vertical axis shows the respondent’s assessment of how often (Always=5, Most of the times=4, Some of the time=3, Rarely=2, Never=1) the individual named above typically: watched children for her (Watch), helped take care of her or the baby in case of sickness (Care), gave guidance about taking care of the baby (Guide), talked with the respondent (Talk), and would give money in case of need (Money). See the original EHB article for other relationships.

The Role of the Spouse: A Critical Relationship. Among all relationships, the one with the baby’s father appeared to be the most important. Women with more support from a loving and helpful partner were at significantly lower risk for depression. Conversely, conflicting or controlling relationships elevated the risk of depression. The baby’s father not only provided the most help but also responded most strongly to his partner’s early signs of depression. This was especially true if the relationship with the mother was one of conflict (a paradox at first, but precisely what is predicted by the bargain idea). This could highlight the evolutionary significance of pair bonding and cooperative parenting.

In ancestral environments, where raising a child often required contributions from both parents (and others), depression could have evolved as a strategy for mothers to secure greater investment from their partner, ensuring the survival of their offspring. Our findings support this idea, suggesting that perinatal depression may indeed catalyze cooperation from fathers and close kin.

Implications for Mental Health and Public Health Policy. While our study provides some evidence for the bargaining model, it’s important to emphasize that the findings do not imply that maternal depression is beneficial or should be left untreated. Depression is a painful condition that requires serious attention and care. However, understanding its potential evolutionary roots could open new avenues for treatment, particularly in the realm of family and marital therapy.

If maternal depression serves as a signal of need within a social group, then interventions that focus on improving relationships and increasing support from family members could be particularly effective. For example, recent research has shown that psychotherapy interventions, such as cognitive behavioral therapy (CBT), can have positive and lasting effects on women’s mental health and their children’s well-being. Our findings suggest that incorporating family therapy, especially to address conflicts with a spouse or other family members, could further enhance these treatments.

Conclusion: Depression as a Call for Cooperation. Maternal depression remains a complex and multifaceted condition. While much of the focus has been on its negative consequences, our research adds to the growing body of evidence suggesting that it may also serve an adaptive function. By acting as a catalyst for increased cooperation, maternal depression might help mothers in challenging environments secure the support they need to care for their offspring.

Understanding depression through an evolutionary lens doesn’t diminish the suffering it causes but offers a deeper perspective on why such a costly condition might exist. As we continue to explore the relationship between mental health and social support, this knowledge could pave the way for more effective treatments that not only address the symptoms of depression but also the underlying social dynamics that contribute to its persistence.

Read the original article: Cassar, A., Schneider, P.H., & Ugwu, C. (2024). Maternal depression as a catalyst for cooperation: evidence from Uganda. Evolution & Human Behavior, 45(4), 106575.