Many thousands of preterm births could be prevented if women with clinical depression receive treatment during pregnancy, researchers say.
The first systematic study of clinical depression during pregnancy has found the psychiatric mood disorder is associated with increased production of the 鈥渕aster鈥� stress hormone, called corticotropin releasing-hormone (CRH), and also with an increased risk of preterm delivery 鈥� the leading cause of infant illness and mortality.
However, other experts warn that taking antidepressants during pregnancy can be risky.
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Veronica O鈥橩eane in the department of perinatal psychiatry at the Institute of Psychiatry in London, UK, and colleagues, recruited two groups of women from thousands attending an antenatal clinic. Among the participants, 28 were diagnosed with severe depression, while 38 were classed as healthy.
O鈥橩eane鈥檚 team measured the levels of different hormones in blood and saliva samples taken from the women throughout the second and third trimesters of pregnancy. They assessed the women鈥檚 mood using standard psychiatric tests.
Over-stimulation
The depressed women had higher levels of CRH in their blood compared to the healthy women. And when they carried out multiple saliva tests during the day, the researchers found that the depressed women had elevated levels of the stress hormone cortisol in the evenings.
Crucially, pregnancy length was significantly shorter, on average, in the depressed women. 鈥淒epression is a major cause of preterm [earlier than 37 weeks] birth, and over-stimulation of stress hormones is at least one cause of this,鈥� O鈥橩eane says.
Postnatal depression is well known, but O鈥橩eane says that depression during pregnancy is a more common 鈥渂ut largely hidden鈥� problem. 鈥淎t least 50% of cases of postnatal depression start during the pregnancy,鈥� she says.
Submissive behaviour
Women are more vulnerable to depression during pregnancy because they are flooded with stress hormones. CRH levels increase naturally during pregnancy, produced and secreted by the placenta.
Animal studies have shown that excess levels can lead to increased 鈥渆motionality鈥� and an exaggerated stress response, as well as social withdrawal and excessive submissive behaviour.
Data in humans is limited, says O鈥橩eane, but what is available suggests that if cortisol levels peak too soon, then babies are born small, and possibly with smaller brains in proportion to their bodies.
Stress carries
The study also showed that babies born to women with depression had lower saliva cortisol responses at eight weeks of age, compared to babies born of non-depressed mothers. This causes the infants to have a 鈥渂lunted鈥� stress response, and may mean they are less able to react to stressful situations.
Maternal stress appears to be transmitted to the next generation, says O鈥橩eane, referring to the ongoing Avon Longitudinal Study of Parents and Children (ALSPAC), conducted by researchers at the University of Bristol in the UK. The children of women in the study who were stressed during pregnancy showed abnormally high levels of the stress hormone cortisol at age 10.
鈥淭his is an inter-generational way of transmitting depression,鈥� says O鈥橩eane. She says that women should not necessarily give up taking antidepressants if they are pregnant, and that physicians should look at a range of treatments, from cognitive behavioural therapy to antidepressants.
鈥淭here is an idea that depressed women should struggle through pregnancy without help, and stay 聭pure鈥�,鈥� says O鈥橩eane. 鈥淏ut depression is a physical disorder and should be treated.鈥�
Judgement call
However, Sophie Corlett of the UK mental health charity, MIND, says there are risks associated with pregnant women taking antidepressants such as selective serotonin reuptake inhibitors (SSRIs). 鈥淚t鈥檚 a judgement call for individuals and doctors according to the severity of the depression.鈥�
In general, women should avoid SSRIs in the first 12 weeks of pregnancy, and reduce the dosage if they are already on the drugs, she says, adding that for severe depression the benefits of taking antidepressants probably outweigh the risks. However, she emphasises that women at risk of depression should seek specialist medical advice.
O鈥橩eane presented her group鈥檚 work on Monday at the Institute of Psychiatry conference on depression, held at the Royal Society of Medicine in London, UK.
