About 15% of women suffer from postpartum depression (PPD). It appears, however, that women with PPD constitute a heterogeneous population.  One difference that we observe clinically is that a subgroup of women with PPD experience depression only during the postpartum period, whereas other women with PPD report a pattern of recurrent depressive illness consisting of both puerperal and non-puerperal episodes.  We suspect that these two subtypes differ from one another, but little study has been devoted to this question.

To better understand these different subtypes of PPD, researchers from Finland compared mothers whose PPD was a recurrence of a prior non-postpartum mood disorder with a group of women for whom PPD was their first (or only) experience of affective illness.   The study group consisted of 104 mothers with postpartum major depression. The Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) was used, and the severity of depression and other psychological symptoms were assessed using several validated rating scales.

The onset of PPD was usually (84%) within six weeks of childbirth. Most women (82%) with PPD had a history of past depression.  What the authors called “pure PPD” was fairly uncommon; only 18% of the mothers with PPD had depressive illness restricted to the the postpartum period.

Although the size of the study was relatively small, the researchers attempted to identify differences between these two populations.  Compared to women with recurrent depression, it appears that the women with pure PPD had somewhat milder depressive symptoms and reported lower levels of hopelessness, somatization, interpersonal sensitivity, anxiety, and suicidal ideation.  

While the Finnish study was small and relied on data collected from a relatively large set of validated rating scales, other studies have taken a different approach to understanding the heterogeneity of postpartum depression, analyzing a smaller range of variables in a larger population.

One such study was published by an international perinatal psychiatry consortium — the Postpartum Depression: Action Towards Causes and Treatment or PACT — which collected data from its 19 member  institutions in seven countries. A total of 17,912 unique subject records were submitted and included data from 13 prospective, four retrospective, and two mixed (prospective and retrospective) studies.  The data were analyzed using a statistical technique called latent class analysis. in a two-tiered approach the researchers assessed the validity of empirically defined subtypes of postpartum depression.

With this approach, the researchers were able to identify three distinct subtypes of PPD.  The most striking characteristics distinguishing the three groups  were severity, timing of onset, comorbid anxiety, and suicidal ideation.

Women in class 1 had the least severe symptoms (mean EPDS score 10·5).  Symptoms typically emerged after delivery.  

Women in class 2 had more severe depressive symptoms  (mean EPDS score 14·8).  Symptoms typically emerged after delivery.  This group tended to report more anxiety symptoms.  In this group, 57% of the women had a history of mood disorder prior to pregnancy, and  46% had a history of anxiety disorder.

Women in class 3 had the most severe symptoms (mean EPDS score 20·1)and were more likely to report suicidal ideation. (63% of the women reported having suicidal thoughts “very often”.)  This group tended to report more anxiety symptoms. This group of women were more likely to experience depressive symptoms early in pregnancy.  Most of the women (83%) had a history of mood disorder prior to pregnancy, and 61% had a history of anxiety disorder.  This group was more likely to report obstetric complications than the other two groups.

In an accompanying commentary, Rubin and Maki noted several limitations of this approach:

The Postpartum Depression: Action Towards Causes and Treatment (PACT) Consortium4 used data aggregated from 19 institutions spanning seven countries. Similar to the field of perinatal research more generally, PACT mainly surveyed white (78%), married or cohabitating women (83%) with a college degree or higher (44%) who do not qualify for government or state assistance (87%). Whether these results generalise to women with low income or minority groups is unknown. The data suggest a high prevalence of perinatal depression for women of low socioeconomic status,and the need to consider risk factors such as drug misuse, early-life stress, and exposure to violence.  Understanding perinatal depression in women from minority groups is of important public health relevance.

How can we use this information?  

As we move toward universal screening for perinatal depression, these studies highlight the importance of asking about history of mood and anxiety disorders prior to pregnancy. Both studies indicate that it is these women that have the most severe depressive symptoms.  The PACT study also supports the recommendations of the American College of Obstetrics and Gynecologists to screen for depression during pregnancy, as well as after delivery, as it is these women that are more likely to have severe depressive symptoms.  

As we design treatment algorithms for women identified with postpartum depression, these studies highlight the importance of tailoring the treatment to the patient.  Women with no history of mood disorder and relatively mild symptoms might benefit from one type of intervention, whereas women with a history of mood disorder and more severe symptoms most likely need a more aggressive approach to treatment.

Ruta Nonacs, MD PhD

Kettunen P, Koistinen E, Hintikka J.  Is postpartum depression a homogenous disorder: time of onset, severity, symptoms and hopelessness in relation to the course of depression.  BMC Pregnancy Childbirth. 2014 Dec 10;14:402.  FULL TEXT

Postpartum Depression: Action Towards Causes and Treatment (PACT) Consortium.  Heterogeneity of postpartum depression: a latent class analysis.  Lancet Psychiatry. 2015 Jan;2(1):59-67.


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