The largest study ever conducted on pregnancy-related nausea and vomiting has revealed links between severe morning sickness and long-term mental health risks, raising what researchers call "very serious" concerns.
The study -- led by King's College London and the South London and Maudsley NHS Foundation Trust -- examined the records of 476,857 pregnant women diagnosed with hyperemesis gravidarum (HG), a condition marked by extreme and persistent nausea and vomiting.
Researchers analyzed anonymized electronic health data from 135 healthcare providers across 18 countries, making it the most comprehensive investigation into HG and mental health outcomes to date.
While nausea is common in pregnancy, HG affects up to 3.6 percent of expectant mothers and is the leading cause of hospital admissions during the first trimester.
Unlike typical morning sickness, HG can cause prolonged vomiting, dehydration, weight loss and malnutrition. Many women report feeling isolated, anxious and unable to function.
A recent study found that more than half have considered terminating their pregnancies due to the severity of their symptoms.
"Hyperemesis gravidarum can be profoundly debilitating," Hamilton Morrin, Doctoral Fellow at the Institute of Psychiatry, Psychology and Neuroscience at King's College London told Newsweek.
"Our data show it roughly doubles the risk of depression and nearly triples postpartum depression."
Researchers investigated 24 neuropsychiatric and mental health outcomes within a year of HG diagnosis.
They found women with HG faced more than a 50 percent increased risk of 13 conditions, including anxiety, depression, post-traumatic stress disorder (PTSD) and postpartum psychosis.
The risks doubled for Wernicke's encephalopathy -- a neurological disorder linked to vitamin B1 deficiency -- as well as refeeding syndrome, eating disorders and depression.
Notably, postpartum depression was 2.7 times more likely in women with HG compared to those without.
"Many of these conditions would warrant urgent referral to specialist services for urgent assessment and treatment to ensure safety of mother and child," Morrin added.
The World Health Organization's ICD-11 classifies HG into "mild" and "HG with metabolic disturbance," the latter involving dehydration, electrolyte imbalance or carbohydrate depletion.
Surprisingly, the study found women with the more severe, physically measurable form of HG actually had a lower risk of depression compared to those with "mild" HG.
This unexpected result suggests physical severity doesn't always align with mental health impact.
Senior author Thomas Pollak, Clinical Reader and Consultant Neuropsychiatrist at King's College London, said the findings highlight a longstanding disconnect between medical assessments and women's lived experiences.
"Our findings show that this gap is not only real but can be very serious," he said. "HG can be associated with severe psychiatric disorders that require urgent recognition and joined-up physical and mental healthcare from the very start of pregnancy."
Morrin advised pregnant women and their families should seek help from healthcare services early if they notice social withdrawal, persistent low mood, anxiety that feels out of control, signs of intrusive or distressing thoughts or any thoughts of self-harm.
"There is a clear need for a collaborative interdisciplinary approach to enable proactive screening, timely recognition and clear referral pathways for providing essential care for severe mental illnesses throughout the perinatal period," he added.