Twenty-two studies (877,181 participants) were included in the review, with 36 comparisons when various outcomes from each study were assessed individually.
Women who had an abortion were more likely to report adverse mental health outcomes compared with women who completed a pregnancy (OR 1.81, 95% CI 1.57 to 2.09). The results were broadly similar when women who had an abortion were compared to women who had a delivery (OR 2.39, 95% CI 1.63 to 3.50), women who had no abortion (OR 1.59, 95% CI 1.36 to 1.86) or women who had an unintended pregnancy (OR 1.55, 95% CI 1.31 to 1.84).
All outcomes were more frequent in women who had an abortion: depression (OR 1.37, 95% CI 1.22 to 1.54), anxiety (OR 1.34, 95% CI 1.12 to 1.60), alcohol use (OR 2.10, 95% CI 1.77 to 2.50), marijuana use (OR 3.50, 95% CI 1.65 to 7.44) and suicide and self-harm (OR 2.55, 95% CI 1.31 to 4.96).
Population attributable fractions were: all outcomes 9.9%, depression 8.5%, anxiety 8.1%, alcohol use 10.7%, marijuana use 26.5%, all suicidal behaviours 20.9% and suicide 34.9%.