People with bipolar disorder (BD) who have experienced childhood trauma (CT) will frequently document having more depressive episodes than manic episodes compared to their non-CT counterparts. Following on from that, there is also speculation on the link between depressive predominance polarity and increased sensitivity to proximal triggers such as stress or sleep disturbances. The resulting biological and physiological impacts from CT are often carried on into adulthood and can manifest as a distal risk factor for increased risk of depressive episodes in BD compared to non-CT counterparts. In the 16 major markets (US, France, Germany, Italy, Spain, UK, Japan, Australia, Brazil, Canada, China, Mexico, India, Russia, South Africa, and South Korea), GlobalData epidemiologists predict there will be 57 million lifetime total prevalent cases of all subtypes of BD by the end of 2025, and that number is estimated to increase to 58.56 million cases in 2030.
BD is a mental illness and individuals who suffer from this condition can alternate between experiencing episodes of mania, or a less intense form of mania called hypomania, and depressive episodes. These periods of elevated mood, excessive energy, talkativeness, insomnia, and increased irritability characterise the mania aspect of BD while the low mood, lack of interest in hobbies, and feelings of guilt and hopelessness characterise the depressive episodes of BD. BD I is defined as those who have experienced at least one episode of mania and BD II as those who have experienced at least one depressive episode and hypomania.
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A prospective, observational cohort study set up in Colombia that followed 73 BD patients with CT and 73 non-CT counterparts for three years was conducted by Hernán Guillen-Burgos and colleagues. The research was published in Nature and found there was a difference in the number of depressive episodes experienced between BD patients with CT and those without; preliminary evidence from the secondary outcomes of the study suggested that depressive episodes, in particular number of episodes, was a mediating factor for predicting poor mental health trajectories and health outcomes.
Over the three-year follow-up period, 689 depressive episodes and 279 manic episodes were recorded. BD patients with CT exhibited earlier onset of the disorder (62.9%), had a higher proportion of early admissions (66.7%), and a higher prevalence of suicidal ideation and behaviour (76.6%). CT exposure also increased the risk of experiencing a cumulative number of depressive episodes by 53%, and after adjusting for confounders, exposure to CT increased the risk of experiencing at least one severe outcome measured by the severity index by 80%.
Participants who were exposed to CT had significantly higher depressive episodes compared to those who were not exposed to CT. BD I patients with CT had an average of 5.88 depressive episodes while those without CT had an average of 3.51 depressive episodes; this difference in the number of episodes was found to be significant. Similarly, those BD II patients with CT suffered a significantly higher number of depressive episodes compared to those without CT, at an average of 6.34 episodes and 2.64 episodes, respectively.
The study quantified that 30.8% of CT’s effect on at least one severe outcome was attributable to depressive episodes and the remaining 69.2% was explained by other mechanisms at play.
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By GlobalDataThese results indicate that CT increased the number of depressive episodes, and that depressive episodes could be a mediator for severe outcomes of BD. The subtype of BD was of clinical relevance when it came to measuring the number of depressive episodes.
