Women with hyperemesis gravidarum, a severe form of morning sickness, are at greater risk of developing mental health problems during and after pregnancy, according to a major international study published Sept. 18 in The Lancet Obstetrics, Gynaecology & Women’s Health.

The study, led by Hamilton Morrin, M.B.B.S., and colleagues at King’s College London, examined anonymized health records of 476,857 pregnant women across 135 health care providers in 18 high- and middle-income countries. Using the TriNetX database, researchers compared outcomes of women diagnosed with hyperemesis gravidarum against those with pregnancies not complicated by the condition.

Results showed significantly higher risks for 18 of 24 mental health outcomes in women with the condition. The greatest risks were linked to Wernicke encephalopathy, refeeding syndrome, postpartum depression, eating disorders, and the need for antipsychotic prescriptions, with relative risks ranging from more than double to nearly triple compared with unaffected pregnancies.

The analysis also noted a reduced risk of pregnancy termination (0.77) among women with hyperemesis gravidarum. No significant association was found for nonaffective psychoses, bipolar disorder, intentional self-harm, or suicide attempts.

“Hyperemesis gravidarum can be associated with severe psychiatric disorders that require urgent recognition and joined-up physical and mental health care from the very start of pregnancy,” said senior author Dr. Thomas A. Pollak of King’s College London.

The findings underscore the importance of comprehensive care for women facing this debilitating condition—addressing not only the physical toll but also the significant psychological risks that accompany it.