Many studies have demonstrated that major depressive disorder has a tendency to convert to bipolar disorder, although it is possible that a reverse shift is masked by treatment. Conversion from unipolar to bipolar disorder generally takes place at a rate of 1% per annum but this may be higher in younger cohorts. Many factors predict conversion, including family history, symptomatology, personality and, in female patients, trigger by childbirth. Clinicians should therefore be aware of the possibility of conversion and conscious of the risk factors.
Keywords: bipolar disorder, major depressive disorder, conversion, switching, depression