Clinical review

Postnatal depression

Peter J Cooper, professor,  Lynne Murray, professor. 

Winnicott Research Unit, Department of Psychology, University of Reading, Whiteknights, Reading RG6 6AL

Correspondence to: Professor Cooper P.J.Cooper{at}reading.ac.uk

There has been considerable recent clinical and research interest in postpartum depression. This has been largely provoked by the accumulating evidence that postnatal depression is associated with disturbances in child cognitive and emotional development.¹ This evidence, which is reviewed below, has renewed concern about the epidemiology of postnatal depression, its aetiology, methods of prediction and detection, and the most appropriate form of management.

	Methods

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This article is based on a review of the recent research concerned with the impact of postnatal depression on child development, and the epidemiology, prediction, detection and management of the disorder. Authoritative recent reviews are cited as well as the most impressive research papers. To supplement our immediate knowledge of the literature we performed literature searches with Medline and PsychLit (1980-97) using the relevant key words ("postnatal/postpartum depression" in conjunction with "infant/child development/outcome, epidemiology, aetiology, prediction, detection and treatment").

	Impact on parenting and child outcome

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There have been several recent prospective studies of samples of women with postnatal depression and their children.¹ They indicate a definite association between the maternal mood disorder and impaired infant cognitive development. Thus, in Cambridge a community sample of children of mothers who had had postnatal depression were found to perform significantly less well on cognitive tasks at 18 months than did children of well mothers, especially the boys. ^{2 3} Two London studies of more socioeconomically disadvantaged populations have found that this effect still obtained when the children were 4-5 years old. ^{4 5} Poor emotional adjustment has been shown to be similarly associated with postnatal depression. Thus, most studies that have systematically examined infant attachment in the context of postnatal depression have found a raised rate of insecure attachments. ^{2 6 7}

There is evidence that these emotional problems persist. A follow up of the Cambridge cohort found that the 5 year old children of mothers who had had postnatal depression were significantly more likely than controls to be rated by their teachers as behaviourally disturbed.⁸ One major conclusion from these studies is that the mechanism mediating the association between postnatal depression and adverse child developmental outcome is the impaired pattern of communication occurring between the mother and her infant.¹

	Epidemiology and course

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Epidemiological studies of puerperal samples have consistently shown that the prevalence of non-psychotic major depressive disorder in the early weeks after delivery is about 10%.⁹ Although this rate does not represent an elevation over the non-postpartum base rate,^10-13 the inception rate for depression does seem to be raised in the first three months postpartum compared with the following nine months. ^{10 13 14} The duration of postnatal depression is similar to that of depressions arising at other timesthat is, episodes typically remit spontaneously within two to six months. ^{9 10} Some residual depressive symptoms are common up to a year after delivery. ^{9 10}

	Aetiology

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There is little evidence to support a biological basis to postpartum depression.⁹ Despite extensive research into steroid hormones in women during the puerperium, no firm evidence has emerged linking these hormones to the development of postnatal depression.¹⁵ It has been suggested that in a small subgroup of those experiencing postnatal depression there might be a thyroid dysfunction.¹⁶ Although this hypothesis merits attention if substantiated, it remains possible that the thyroid dysfunction could be secondary to immunological changes brought about by stress.

The presence of maternity blues in the period immediately post partum has been found to be related to the subsequent development of postpartum depression, but no hormonal basis to this association has been identified. ^{9 15} Obstetric factors are important in a vulnerable subgroup of women: among those with a history of depressive disorder, complications during delivery are associated with a raised rate of postnatal depression. ^{17 18}

The consistent finding of the epidemiological studies carried out to date is that the major factors of aetiological importance are largely of a psychosocial nature.⁹ So, the occurrence of stressful life events in general and unemployment in particular, the presence of marital conflict, and the absence of personal support from spouse, family, and friends have all consistently been found to raise the risk of depression post partum.

A psychiatric history is also commonly reported to be a risk factor for postnatal depression, especially a history of depressive disorder. This latter association has recently been clarified in a five year follow up of a cohort of primiparous women who had had a postpartum depression as a recurrence of previous non-postpartum mood disorder and a cohort for whom the postpartum depression was their first experience of affective disturbance.¹⁹ The first group were found to be at greater risk for subsequent non-postpartum depression but not to be at risk for depression after a subsequent delivery. Conversely, the second group were found to be at greater risk for subsequent postpartum depression but not for subsequent non-postpartum depression. This suggests that for a subgroup of those with postpartum depression the puerperium carries specific risk, for either biological reasons or psychological ones surrounding the demands of infant care.

	Prediction

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Although several studies have reported on antenatal factors associated with postnatal depression, all but one have been based on samples that were too small to derive a reliable predictive index. The single large scale predictive study to be conducted revealed that the most reliable predictors of postpartum depression (such factors as the absence of social support and a history of depression) each approximately double the odds over the base rate risk.²⁰ The predictive index derived from this study of several thousand women is of some use: at a cut off score with a sensitivity of 75% the specificity is 52%, and at a cut off score with a specificity of 75% the sensitivity is 44%. It is unlikely that there could be much improvement on the positive predictive value of this instrument using only antenatal factors.

Prediction of postpartum depression could be improved if account were taken of certain postpartum factors. Thus, in a recent study of the impact of neonatal factors on the course of maternal mood it was found that, over and above the predictive contribution of antenatal factors, both a high score for "maternity blues" and certain neonatal factors (irritability and poor motor control) were significantly related to the onset of postnatal depression.²¹ Since both the blues and the neonatal factors contribute predictively over and above the predictive antenatal variables, the positive predictive value of the collective critical antenatal factors could be augmented by taking account of both these postpartum variables.

	Detection

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Postpartum depression is often missed by primary care teams. ^{22 23} Its detection does not, however, present any special problem. The clinical features of the disorder are not distinctive,^9-11 and its assessment is straightforward. Indeed, a simple brief self report measure, the Edinburgh postnatal depression scale (EPDS) has been developed as a screening device.²⁴ It has sound psychometric properties. A large community study has revealed a specificity of 92.5% and a sensitivity of 88%.²⁵ The questionnaire is easy to administer, simple to interpret, and could readily be incorporated within the routine services provided to all postpartum women. Sensitive clinical inquiry in high scorers would be sufficient to confirm the presence of depression.

	Treatment

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Drug treatment
There has been little systematic research on the drug treatment of postnatal depression. Although progesterone treatment has been advocated,²⁶ there has been no systematic evaluation of its clinical usefulness. The efficacy of oestrogen treatment has, however, recently been evaluated in a placebo controlled trial.²⁷ In a sample with severe and chronic postpartum depression, mood improved in both groups but significantly more so among those receiving oestrogen than among those receiving placebo. The appropriateness of this form of treatment in more typical samples of postnatally depressed women remains to be evaluated.

Psychological treatment
There have been three controlled trials of psychological treatment of postpartum depression. Holden et al found that women visited by health visitors trained in non-directive counselling, an average of nine visits over 13 weeks, showed substantially greater improvement in maternal mood than did the control group receiving routine primary care.²⁹ Similarly, a significant benefit in terms of remission from depression has been found for six weekly counselling visits by child health clinic nurses in Sweden.³⁰ Finally, a recent controlled evaluation of three brief, home based, psychological forms of intervention (including a session of non-directive counselling) found that they improved maternal mood.³¹

Treatment and the mother-infant relationship
Few studies have examined the impact of treating postnatal depression on the quality of the mother-infant relationship and child development. One controlled trial of psychological treatment found that the intervention was associated with significant improvement in maternal reports of infant problems, both immediately after treatment (four to five months post partum) and at 18 months post partum.³¹ In addition, early remission from depression, itself significantly associated with treatment, was related to a reduced rate of insecure infant attachment at 18 months. Similar benefits have been reported in a study of health visitors' practice.²³ When training was provided to all the health visitors working in one NHS sector a cohort study was conducted, with assessments made of the health visitors' clientele both before and after the training. Treatment significantly improved both maternal mood and the quality of the mother-infant relationship.

	References

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27. Gregoire AJP, Kumar R, Everitt B, Henderson AF, Studd JWW. Transdermal oestrogen for treatment of severe postnatal depression. Lancet 1996; 347: 930-933[Medline].
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