Research in context
Evidence before this study
We searched MEDLINE, PsycINFO, and Embase databases for articles in English and published before Jan 1, 2015, that tested the association of childhood maltreatment with clinical features and course of illness in bipolar disorder, using the search terms “child* abuse”, “child* neglect”, “child* maltreatment”, “early abuse”, “early maltreatment”, “early neglect”, “sexual abuse”, “physical abuse”, “emotional abuse”, and “family conflict” in combination with “bipolar”, “mania/manic”, “hypomania/hypomanic”, “cyclothymia/cyclothymic”, and “manic depress*”. After excluding duplicates or unsuitable reports, we identified 30 studies that tested the association of a history of childhood maltreatment with 12 correlated clinical outcomes in patients with bipolar disorder.
Added value of this study
From our 12 independent meta-analyses, we showed that, compared with patients with bipolar disorder who did not experience childhood maltreatment, patients with bipolar disorder and a history of childhood maltreatment had greater mania severity, greater depression severity, greater psychosis severity, higher risk of comorbidity with post-traumatic stress disorder, anxiety disorders, substance misuse disorders, and alcohol misuse disorder, earlier age of bipolar disorder onset, higher risk of rapid cycling, greater number of manic episodes, greater number of depressive episodes, and higher risk of suicide attempt. Effect sizes varied across outcomes with odds ratios of 1·26 to 3·60. Overall, these associations were not accounted for by artifacts owing to publication bias, undue effect of individual studies, or variation in study quality.
Implications of all the available evidence
Results suggest that a history of childhood maltreatment can be used as an indicator for disease progression to identify patients with bipolar disorder who are at a higher risk of unfavourable clinical features and course of illness. Additional research is needed to test whether a history of childhood maltreatment can be used as an indicator for unfavourable treatment outcomes. Further research on the stratified, and possibly trans-diagnostic, biological abnormalities associated with a history of childhood maltreatment could uncover innovative treatment strategies.