Is there a neuropsychology of pregnancy ?

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  During pregnancy,  both estrogen and progesterone concentrations steadily climb up to levels far beyond the peak of the menstrual cycle.   Then,  at parturition,  both hormones immediately (perhaps even brutally) drop to the low menstrual level.    There have been several studies of neurotransmitter metabolites in human serum during the stages of pregnancy.   These vary predictably:  since estrogen is a serotonin agonist and a dopamine antagonist,  we would expect the former neurotransmitter to steadily increase and the latter to steadily decrease  -until parturition produces a bounce-back.  This is exactly what occurs.   Who hasn't heard of postpartum depression ?  It is a depressive state frequently encountered by women who's neuroendocrine interface cannot adapt to such a brutal drop in estrogen level as occurs at parturition.   This disorder affects a whopping 10-15% of parturating women,  and is most probably serotonin-mediated.   Crying is not enough to qualify for the diagnostic label of depression.  It is nevertheless impressive that 67% of women experience crying spells within 10 days after having given birth.   Not all of the effect of giving birth on mood should be attributed to hormonal upheaval however.   Women who adopt an infant also frequently report a downturn of mood.   After all,  within 10 days a mother typically has to exchange her freedom for that of the infant.  As for dopamine,  the lurking danger would be for a schizophrenic episode because brain dopamine metabolism climbs up so quickly at parturition,  challenging the neuroendocrine interface as well.    This disorder is fortunately much rarer than is post-partum depression.  However, whereas men's risk for a schizophrenic episode declines after the age of 40,  women's risk increases several-fold.    For example,  a woman who has had a post-partum schizophrenic episode has a 65% chance of undergoing one again at menopause  -at a time when brain dopamine climbs up again,  and stays up. 

It appears that the hormonal changes occurring during pregnancy have a protective effect against behavioral breakdown resulting from brain lesions.  In one experiment,  three groups of female rats received the same brain lesion.  One group was non-pregnant,  one was pregnant,  and the third was pseudo-pregnant (estrogen treated).  The animals were tested on a maze-learning task prior to and after the lesion.  The pseudo-pregnant females recovered best on this task,  followed by the pregnant females,  and the group differences were statistically significant.  In short,  circulating hormones seem to protect females against infection,  as well as perhaps a few other brain lesion sequels which remain to be determined.

Another neurobiological way of investigating the relationship between pregnancy and brain function is to determine whether parity (the number of children a woman has given birth to) modulates risk factors for behavioral disorders resulting from brain diseases.  Indeed,  having children subsequently reduces a woman’s production of sex steroids,  both masculine and feminine. One epidemiological study examined the contribution of childbearing to the sex difference in first admission rates for affective psychosis. The effects of sex, age, marital status and parity on first admission rates are examined in 114 patients admitted from a defined catchment area. The rate of first admission in women was almost twice that in men. Using logistic regression analysis (a statistical technique capable of determining which of several predictors best explain a criterion) one significant factor accounting for this sex difference emerged: female parity. The effect of parity was evident up to the age of 54, and it accounted entirely for the sex difference in relative risk. Nonparous women had a lower relative risk of admission than men.  An apparent effect of marital status was significant only in women, and was accounted for by parity and age.   Another investigation found a weak relationship between parity and schizophrenia:  the risk for this disease increases slightly with increasing parity.   This research theme is a good example of a neurobiological approach which could easily be confounded by sociocultural factors.   In many women in the world today (surely in most),  increasing parity adds biological, social, financial and psychological stress.   Increasing risk for mental disease as a function of parity could be easily explained by factors which are not primarily biological,  i.e.,  which are do not specifically consist of a gonadal hormone effect on brain function.    For example, a large scale study of mono and dizygotic twins found that parity was not a predictor of psychiatric disease per se,  but rather,  that  conjoint «marital stress» variables (obviously associated with parity)  were the main contributive factors.     Indeed,  parity of men actually extends life expectancy and that of women reduces it.  This could well be related to segregation of roles as a function of parity:  having more children stresses women more than it does men.  I predict however,  that with the trend we see toward full penetration of women into the job market (egalitarianism in extrafamilial work),  evolution of parental roles will quickly follow (egalitarianism in intrafamilial work).    Parity will have effects which will be decreasingly sex-segregated  with the years to come.    Men will become increasingly stressed by paternity and will pay for it in their health.