The meta-analysis of 22 major abortion studies found that women who delivered an unplanned pregnancy were significantly less likely to have mental health problems than similar women who aborted unplanned pregnancies. 

Women with a history of abortion were 55 percent more likely to have mental health problems than women who did not abort an unplanned pregnancy.

Using a standardized statistical technique for combining the results of multiple studies, the meta-analysis revealed that women with a history of abortion face higher rates of anxiety (34 percent higher) and depression (37 percent higher), heavier alcohol use (110 percent higher) and marijuana use (230 percent higher), and higher rates of suicidal behavior (155 percent higher).

[Coleman PK. Abortion and mental health: quantitative synthesis and analysis of research published 1995–2009. The British Journal of Psychiatry (2011) 199, 180–186]