Childhood trauma is highly prevalent in patients with bipolar disorder (BD) and has been associated to a more severe/complex expression of the disorder. Little is known about the familial and individual factors that can mediate the occurrence of trauma within families but also influence the outcomes of BD. We will present data from two independent samples of patients with BD in order to identify the potential mediators for occurrence and severity/complexity. In a first sample of 371 patients with BD, 256 relatives and 157 healthy controls, we will show that there is a familial resemblance for emotional and physical abuses. Patients’ level of physical abuse was associated with their parental levels of physical abuse, but also with their father's history of alcohol misuse (p < 0.05). Second, in a sub-sample of 270 normothymic patients, we have performed a path-analysis to demonstrate that emotional and physical abuses interacted with cannabis misuse to increase the frequency of psychotic features and delusional beliefs. Finally, in an independent sample of 485 euthymic patients from the FACE-BD cohort we used path-analytic models to show that emotional abuse increased all the assessed affective/impulsive dimensions (p < 0.001). In turn, affect intensity and attitudinal hostility were associated with high risk for suicide attempts (p < 0.001), whereas impulsivity was associated with a higher risk for presence of substance misuse (p < 0.001). These results illustrate that childhood trauma might derive from parental characteristics (own childhood trauma and psychopathology) and increase the severity/complexity of BD through individual dimensions of psychopathology.