Background Psychological illness occurring in association with hyperemesis gravidarum (HG) has been widely reported.Objective To determine if there is a higher incidence of psychological morbidity in women with HG compared with women without significant nausea and vomiting in pregnancy.Search strategy PubMed, MEDLINE, Embase and PsychINFO were searched up to September 2015.Selection criteria Articles referring to psychological morbidity in relation to HG. For meta-analysis case-control studies using numerical scales to compare psychological symptoms.Data collection and analysis Articles were independently assessed for inclusion by two reviewers and methodology was appraised using the Newcastle Ottawa Scale. Comparison was made using the standard mean difference (SMD) in symptom scale scores.Main results In all, 59 articles were included in the systematic review, 12 of these were used in the meta-analysis. Meta-analysis of depression scale scores demonstrated a very large effect with statistically significantly higher depression scale scores in women with HG (SMD 1.22; 95% CI 0.80-1.64; P ≤ 0.01) compared with controls. Meta-analysis of anxiety scores demonstrated a large effect with statistically significantly higher anxiety disorder scale scores in women with HG (SMD 0.86; 95% CI 0.53-1.19; P ≤ 0.01). In both analyses significant heterogeneity was identified (depression and HG I 2 = 94%, P ≤ 0.01; anxiety and HG I 2 = 84%, P = 0.02).Conclusions Our systematic review and meta-analysis have shown a significantly increased frequency of depression and anxiety in women with HG. The findings should prompt service development for women with HG that includes provision of psychological care and support.Keywords Anxiety, depression, hyperemesis gravidarum, pregnancy, sickness, vomiting.Tweetable abstract Meta-analysis demonstrates an increase in #PsychologicalMorbidity in women with #HyperemesisGravidarum Please cite this paper as: Mitchell-Jones N, Gallos I, Farren J, Tobias A, Bottomley C, Bourne T. Psychological morbidity associated with hyperemesis gravidarum: a systematic review and meta-analysis. BJOG 2017;124:20-30.