Severe pregnancy sickness raises risk of some mental health conditions

Severe pregnancy sickness raises the risk of developing some mental health conditions by over 50 per cent, a new study suggests.

Researchers found that women with hyperemesis gravidarum (HG) or severe pregnancy sickness had over 50 per cent higher risk of 13 neuropsychiatric and mental health conditions, including postpartum psychosis and post-traumatic stress disorder (PTSD).

The risk of developing mental health conditions significantly increased postpartum depression, which was found to be over 2.7 times more likely when women experienced HG.

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The work was undertaken by researchers at King’s College London (KCL) and the South London and Maudsley NHS Foundation Trust. The study, published in The Lancet, is the first to explore neuropsychiatric and mental health outcomes for women with HG.

HG, which can lead to dehydration and weight loss, as well as mental health deterioration, including anxiety and depression, and affects around 3.6 per cent of pregnancies. It is the most common reason for hospitalisation in the first trimester of pregnancy, and nearly half of women who experience HG are so severely affected that they consider terminating their pregnancy. Socioeconomic deprivation and ethnicity can put some women at a higher risk of developing the condition, as can specific comorbidities, including thyroid disease and diabetes and a sensitivity to the hormone GDF-15.

The retrospective cohort study compared women with HG to pregnant women without HG, analysing how many developed any of 24 mental health or neurological conditions in the year after their diagnosis of HG. It is the most extensive investigation of HG, analysing work between 2010 and 2025, and including nearly half a million women (51 per cent of whom were White and 24 per cent of whom were Black) across 35 healthcare providers in 18 countries.

For 13 of the mental health and neurological conditions, women with HG were at least 50 per cent more likely to develop these conditions compared to women without HG, including postpartum psychosis and post-traumatic stress disorder (PTSD). For other, less common conditions such as Wernicke’s encephalopathy, a brain disorder caused by vitamin B1 deficiency or refeeding syndrome, a complication when nutrition is reintroduced too quickly after malnourishment, and eating disorders, the risks for women with HG were much higher and in some cases double or more. The chance of developing depression, particularly postpartum depression, was found to be 2.7 times more likely in women with HG compared to those without it.

No increased risk was found for non-affective psychoses such as schizophrenia, non-psychotic bipolar disorder, intentional self-harm or suicide attempts for women with HG.

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Dr Hamilton Morrin, a doctoral fellow from KCL, explained that HG goes far beyond common pregnancy sickness and can be profoundly debilitating. He said: ‘Whilst we already knew from previous research that women with HG are at an increased risk of anxiety, depression and PTSD, our study demonstrated an increased risk of severe mental health conditions, including psychosis and eating disorders. Many of these conditions would warrant urgent referral to specialist services for urgent assessment and treatment to ensure safety of mother and child.’

The researchers also examined the impact of ‘mild HG’ and ‘HG with metabolic disturbance’, a subcategory used in the ICD-11, the latest International Classification of Diseases by the World Health Organization, where the latter is perceived as more severe. Researchers found that ‘mild HG’ was associated with a higher risk of depression, whereas ‘HG with metabolic disturbance’ showed significantly reduced risk of depression compared to mild HG.

‘What we found is that the internationally recognised categorisation of HG based on metabolic disturbance works well to identify individuals who require treatment for their physical health, but may not always be suitable for identifying those in need of mental health support. The severity of HG does not directly correlate with the degree of impact on mental health. As clinicians, we have a responsibility to ensure these women receive adequate integrated care across both physical and mental health,’ Dr Hamilton Morrin explained.

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The researchers say the findings show that HG can be associated with severe psychiatric disorders, ‘requiring urgent recognition’, as well as  joined-up physical and mental healthcare from the start of pregnancy.