Attachment, development and the Surgeon General

It will not be denied, that a child, before it begins to write its alphabet and to gain worldly knowledge, should know what the soul is, what truth is, what love is, what powers are latent in the soul.

Mohandas Gandhi, 1927

One of the most significant statements in the recently released Surgeon General’s Call to Action is the recommendation that our society “work toward establishing paid maternity leave for all employed mothers.” ¹ The acknowledgement that the absence of paid leave is a barrier to breastfeeding is of monumental significance.   Without paid leave, it seems highly unlikely that our society will ever be able to come close to achieving the now universally accepted recommendations to breastfeed exclusively for 6 months, and to continue to breastfeed after the addition of complementary foods until the infant is at least one year of age.   Although strategies that enable mothers to express their milk while at work are certainly laudable, it is far more preferable to put the infant to breast than to offer breast milk in a bottle.   In other words, it is best to keep mothers and infants together as much as possible, for as long as possible.   This can only happen by guaranteeing employed mothers a paid maternity leave.

But how can we convince the leaders of our society that a guaranteed paid maternity leave is the way to go? How can we make the case for a paid leave policy? At a time when employee benefits are being pared down and social insurance measures are under assault, the prospect for the adoption of a paid leave policy, voluntary or otherwise, seems very dismal indeed.   Simply arguing that a paid leave should be supported because of its positive impact on breastfeeding is not likely to influence the thinking of our policy makers.   We must find a more compelling argument.

Maybe we should assert that a paid maternity leave should be supported just because it’s the right thing to do.   The United States is one of only four nations in the world that does not have a paid leave policy.   Every other nation recognizes that society has a special obligation to support a family whose employed mother takes time off from work to care for her newborn infant.   The United States recognizes no such obligation.   This is a reprehensible position, but arguing that a maternity leave should be supported on ethical grounds alone is unlikely to make much of a difference; after all, ever since 1979, the United States has managed to ignore the United Nations Convention on the Elimination of All Forms of Discrimination, which called on all nations to establish a paid maternity leave policy.   There is no reason to assume that the nation’s leaders will undergo a sudden change of heart in the foreseeable future.

There is also the argument that a paid maternity leave will contribute to a reversal in the trend toward declining fertility rates in developed countries, a phenomenon that threatens the future of such “pay as you go” social insurance programs as social security.^2,3 However, this argument is debatable and unlikely to be sufficiently compelling to make much of a difference.   But there remains one argument that could seal the deal in favor of paid leave: a paid maternity leave policy may well turn out to be an extremely important public health issue.

At birth, the cranium of the newborn infant is only a quarter of the size of the adult cranium⁴.   Most of the growth and development of the brain takes place after birth: “… the brain growth spurt… begins in the last trimester of pregnancy and continues to 18 to 24 months of age.”⁵ As a result of this neural immaturity, “the cellular architecture of the cerebral cortex is sculpted by input from the social environment embedded in the early attachment relationships.”⁵ In a very real sense, the development of the brain is highly dependent upon the interaction of the infant with its environment, particularly its attachment to the mother.   The quality of that relationship is bound to be impacted by the amount of time the mother and infant are allowed to be together.   Ample time to be with the infant is the one thing most employed mothers simply do not have.

In the 1960’s, 63% of employed pregnant women would quit work before delivery.   By the 1980’s, only 27% left work.   Also in the 1960’s, only seventeen percent of those women who returned to work did so within twelve months of delivery, whereas in the 1990’s, 60% of employed mothers returned to work within 6 months of delivery, half of these within 3 months⁶.   The huge number of mothers leaving home so soon after delivery in order to return to work is a phenomenon unprecedented in history, and indeed it would be surprising if such an event did not have very serious public health repercussions.

Those of us who have practiced primary care pediatrics over the last twenty to thirty years have witnessed an alarming rise in the number of children afflicted with extremely serious psychosocial disorders, including major depressive disorder, bipolar disorder, anxiety, attention deficit disorder, and autism spectrum disorders.   What is happening? Can this striking rise in neurodevelopmental pathology be nothing more than the expected response to a number of discrete, unhealthy social dislocations? Or is there something more primordial in play? At least to some degree, can these disorders be traced back to some kind of insult to the developing limbic system, perhaps a deprivation of the trophic effects of maternal attachment so necessary for normal neurodevelopment?

“Synapses appear to be programmed to be eliminated if they are not functionally confirmed, based on some not fully known aspects of their activity history.   In general, frequently active connections… are more likely to survive…   The effects of experience on these systems – normal or abnormal -become increasingly irreversible over time.”⁷ In the case of the limbic system, as Schore notes, the “experience” consists primarily of the mother-infant attachment.   The pruning of the limbic system may be most pronounced over the course of the first full year of life, during which time the synapses of the prefrontal cortex (part of the limbic system) continue to proliferate, if experientially stimulated ⁷.

One possible clinical example of maldevelopment of the limbic system is a mood disorder.   Mood disorders are not situational in etiology.   They don’t appear simply as a result of a maladaptive response to a specific crisis.   Rather, they relate to a derangement in how the brain, and specifically the limbic system of the brain, is wired, a derangement that may well extend backward in time to early infancy.   There is likely a genetic predisposition, particularly with respect to Bipolar Disorder, but the expression of the problem, not becoming manifest until decades later, may depend upon an environmental trigger.   Perhaps that trigger consists of a reduced synaptogenesis, or a pathological pruning of the meso-limbic or meso-cortical pathways of the limbic system, resulting in turn from limited mother-infant interaction.

We come full circle, back to breastfeeding.   Breastfeeding is the quintessential manifestation of mother-infant attachment.   There are few instances of an act more intimate than the nourishing of an infant from one’s own body.   In the context of this discussion, it is intriguing that oxytocin plays an important role as a neurotransmitter in the limbic system ^8. In the act of breastfeeding, oxytocin levels rise in the mother and the infant alike⁹.   It seems reasonable to presume that at least a number of limbic system pathways will grow or decay in direct proportion to oxytocin-mediated stimulation.   Indeed, the effect may be of little significance in most humans, but if there is a genetic predisposition to pathway atrophy (for example, a reduction in the number of oxytocin neuroreceptors), the final result may be a pathological change in behavior.

For example, there is the diagnosis of anxiety disorder.   Fear and anxiety are housed in the amygdala, a prominent nucleus in the limbic system.   Activation of the amygdala is modulated and down-regulated by oxytocin^{10, 11}.   It’s interesting to speculate that inadequate development of these negative feedback systems involving the amygdala (due to inadequate mother-infant interaction) may conceivably give rise to an anxiety disorder, which for reasons that remain unclear may not express itself until later in life.

Administration of oxytocin has been found to ameliorate the symptoms of patients with autism spectrum disorder^{12, 13}.   The relief is incomplete and transient; but suppose the developing limbic system in genetically predisposed infants were to be bathed in oxytocin during the first few months of life, before the “window of opportunity” for the development of social affiliation pathways closed shut, never to be opened again? Could the emergence of autism be prevented by adequate breastfeeding, at least in some of these infants?

Another nucleus in the limbic system is the hippocampus.   Among other things, the hippocampus is largely responsible for learning and memory.   Hypoplasia of projections from the hippocampus may result in impairment of these functions.   Suppose our hypothesis is correct that the development of the limbic pathways depends in large measure upon the degree and duration of the mother-infant attachment.   Then is it possible that insufficient attachment could result in an impairment of learning?   Such an argument would be difficult to prove, but Baum was able to demonstrate a negative relationship between the number of hours a mother worked per week during the first year of the life of her infant, and the scores on Peabody Achievement tests performed when the child was 3 to 5 years of age or older.   When the data were controlled for family income, the negative correlation between the number of hours worked and subsequent performance on achievement tests actually strengthened¹⁴.

We could carry this speculation even further.   When I was young, I was deeply moved by the humanistic psychology of Maslow, May, and Lang.   These thinkers argued eloquently that psychological health meant more than being content and well-adjusted.   It is not enough for the mind to strive for zero balance.   There is more to life than that.  As Maslow said, “What shall we think of a well-adjusted slave?”¹⁵

Since the days of humanistic psychology, the paradigm for psychological health has shifted.   Today, the brass ring appears to be freedom from pain and stress; the goal is contentment.   It might be fine to settle for contentment, if you happen to be a cow.   But people, presumably, are different.   People seek, or should seek, a transcendent meaning in their lives, something that enriches it and makes it worth living.   That sense of thankfulness of purpose finds its home in the nucleus accumbens septi, another limbic system nucleus.

To the extent that we have stopped talking about self-actualization as a benchmark of psychological health, we have truly lost something.   The shallowness of values commonly encountered in contemporary living is doubtlessly multifactorial in its causation, but to a great degree, the pervasive loss of a deeper sense of purpose in life may ultimately have its roots in the disruption of the developing limbic system, owing to the premature separation of mother from infant, a ubiquitous and tragic consequence of the rapid return of the working mother to her place of employment.

All of the forgoing arguments are entirely hypothetical, yet at the least they warrant serious attention and research.   At long last, our society has to turn its attention to the possible health consequences of inadequate maternity leave.   If it turns out that such consequences do indeed obtain, then the argument for a paid maternity leave policy becomes all the more compelling and will require urgent redress.

Jerry Calnen, MD, FABM is a pediatrician and president of the Academy of Breastfeeding Medicine.

Posts on this blog reflect the opinions of individual ABM members, not the organization as a whole.

Note: most of the discussion on the anatomy of the limbic system is based upon Jeannette Nordon’s excellent course, Understanding the Brain (The Great Courses. Chantilly, VA, 2007).   I highly recommend it. – GC.

1. The Surgeon General’s Call to Action to Support Breastfeeding. 2011.

2. Averett SL and Whittington LA. Does maternity leave induce births? Southern Economics Journal 2001;68:403-417.
3. Winegarden CR and Bracy PM. Demographic consequences of maternal-leave programs in industrial countries: evidence from fixed-effects models. Southern Economics Journal 1995;61:1020-1035.
4. Trevethan WR, McKenna JJ. Evolutionary environments of human birth and infancy: insights to apply to contemporary life. Children’s Environ 1994;11:13-36.
5. Schore AN. Attachment, affect regulation, and the developing right brain: linking developmental neuroscience to pediatrics. Pediatrics in Review 2005,26:204-211.
6. Smith K, Downs B, O’Connell M. Maternity Leve and Employment Patterns: 1961-1995. U.S. Census Bureau, Current Population Reports, Washington, DC, 2001.
7. Shonkoff JP and Phillips DA, eds. From Neurons to Neighborhoods. The Science of Early Childhood Devedlopment. National Academy Press, Washington, D.C., 2000, p 189.
8. Insel TR and Young LJ. Neuropeptides and the evolution of social behavior. Curr Opin Neurobiol. 2000;10:78-789.
9. Klaus M. Mother and infant: early emotional ties. Pediatrics 1998; 102;e1244-1246.
10. Kirsch et al. Oxytocin modulates neural circuitry for social cognition and fear in humans. J Neurosci 2005; 25: 11489-11493.
11. Baumgartner T, Heinrichs M, Vonlanthen A, Fischbacher U, Fehr E. Oxytocin shapes the neural circuitry of trust and trust adaptation in humans. Neuron. 2008; 58: 639-650.
12. Hollander E et al: Oxytocin infusion reduces repetitive behaviors in adults with autistic and Asperger’s disorders. Neuropsychopharmacology 2003; 28:193-198.
13. Hollander E et al: Oxytocin increases retention of social cognition in autism. Biol Psychiatry 2007; 61: 498-503.
14. Baum CL. Does early maternal employment harm child development? Journal of Labor Economics. 2003; 21(2): 409-448.
15. Maslow AH. Toward a Psychology of Being (2nd ed.). D. Van Nostrand Co., Princeton, NJ, 1968, p. 8.