Kessing LV, et al. – This systematic review and meta–analysis aimed to determine the rate and predictors of conversion from unipolar to bipolar disorder. It was observed in the findings that the conversion rate from unipolar to bipolar disorder reduces with time. It was not feasible to identify predictors of conversion that was consistently or mainly confirmed across studies, which might be due to variations in methodology across studies.

Methods

• A systematic literature search up to October 2016 was performed in this research.
• For the meta-analysis, the authors only included investigations that utilized survival analysis to estimate the conversion rate.

Results

• An aggregate of thirty one studies were identified, among which eleven utilized survival analyses, including two register-based studies.
• Findings revealed that the yearly rate of conversion to bipolar disorder diminished with time from 3.9% in the first year after study entry with a diagnosis of unipolar disorder to 3.1% in years 1-2, 1.0% in years 2-5 and 0.8% in years 5-10.
• A sum of 8 risk factors were assessed including gender, age at onset of unipolar disorder, number of depressive episodes, treatment resistance to antidepressants, family history of bipolar disorder, the prevalence of psychotic depression, the prevalence of chronic depression, and severity of depression.
• It was impractical to distinguish risk factors that were consistently or mainly confirmed to predict conversion across studies.