2. 2. Methodological issues
Three methodological issues need to be considered in discussing bipolar prodromes.
First, as stated above, some bipolar patients never recover hilly from an acute depressive episode and suffer from residual symptoms. Furthermore, it has also been reported that even for patients who did not relapse over an average follow-up of 4.3 years, 46% continued to report significant levels of affective symptomatology (Gitlin et al., 1995). In another study, it was reported that, over a mean of 12.8 years of follow-up, bipolar patients continued to experience subsyndromal symptoms of which depression symptoms were predominant (Judd et al.. 2002). Clinically, residual symptoms may intensify and become prodromal symptoms. which may be quantitatively hut not qualitatively different from thesymptoms in a full bipolar episode. It is, thus, difficult for these patients to decide when residual symptoms may become prodromal symptoms or where the prodromal phase ends and the full-blown illness begins.