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According to Wikipedia, Major depressive disorder (MDD), also known simply as depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Now, while depression can affect anyone, at any time, women are twice as likely to experience major depression in their lifetime than men.
The question is: does depression look different at different times in women? Will a depressive episode that occurs in early adolescence be different from depression that appears postpartum? This has been a question that has sparked many debates for a long time (150 years, to be exact!). The question is important because if postpartum depression (PPD) is not considered a distinct disorder, then screening, referral for treatment, and research regarding prevention and drug development will not be targeted and this will lead to missed opportunities to support women properly at this time.
So, what does the latest research tell us in how MDD differs from postpartum (or 'perinatal' which starts from pregnancy and lasts 12 months postpartum) depression? Here are a few fascinating similarities and differences:
Symptoms: while both major depressions at other times and perinatal depression symptoms are heterogeneous (i.e, no two individuals have the exact same symptoms), the symptoms differ in the timing of when they appear during the perinatal phase. E.g, women who experience depression within 8 weeks after giving birth have more severe symptoms compared to women who start feeling depressed during pregnancy. The depression that starts after birth is also more the anxious type of depression where there is the loss of interest in anything that gives pleasure.
Genetic factors: While 'normal' depression and postpartum depression share two-thirds of the same genetic risk factors, postpartum depression has higher heritability than MDD, and here too, the timing of when the depressive episode starts in the postpartum period affects how strongly genetics predict if someone will have PPD. For example, genetics contribute more to PPD in the early postpartum period (within 6–8 weeks postpartum) than in the late postpartum period.
Hormonal factors: Changes in the hormonal levels and their effect on the HPA-axis in the brain plays a major role in depression at any time as well as in PPD. However, what is interesting is that it is not the levels of the hormones as much as the sensitivity to the dramatic hormonal fluctuations during pregnancy and after giving birth (rise and fall) that makes a woman be at higher risk for PPD.
Psychosocial factors: While chronic stress and strain contribute to both 'normal' depression and PPD, childbirth and infant care are psychosocial stressors that are unique to the postpartum period. Timing has an important contribution here too: Parenting stress at 6 weeks postpartum is associated with PPD at 3–6 months postpartum.
Currently, it remains an open question whether PPD is a biologically distinct disorder from major depressive disorder, but researchers are forming consortiums (e.g., Action towards Causes and Treatment (PACT)) to tackle these difficult questions. It is evident though that perinatal depression differs quite significantly in the timing of depression onset. Major depressive episodes that begin early postpartum seem to be driven by biological factors that are triggered by hormonal changes, whereas psychosocial stressors may be more relevant triggers for major depressive episodes that begin late in the postpartum period.
As per the article below, regardless of whether sufficient evidence exists to consider PPD to be a distinct disorder, there are likely benefits to treating early-onset PPD as if it were distinct from a major depressive disorder. For example, a separate diagnosis for PPD might lead to more effective screening and greater support for investments in research and development of treatments specifically targeting major depressive episodes with onset during the early
postpartum period. Currently, the standard of care for postpartum medical follow-up is at 6 weeks postpartum, which would be inadequate for helping women with the onset of illness during the first month following delivery.
At Haplomind, we do not view 'perinatal depression' as another major depressive disorder but are studying the nuances of what makes it different so that we can offer a more tailored screening and treatment for diagnosing and treating perinatal depression.
Further reading: https://focus.psychiatryonline.org/doi/10.1176/appi.focus.20190045