Background: Systematic studies addressing symptoms, signs and temporal aspects of initial bipolar prodrome are reviewed to identify potential clinical targets for early intervention.
Methods: The databases PsycINFO, PubMed, EMBASE and British Nursing Index were searched for original studies.
Results: Eight studies were identified. Irritability and aggressiveness, sleep disturbances, depression and mania symptoms/signs, hyperactivity, anxiety, and mood swings are clusters representing common symptoms and signs of the distal prodrome of bipolar disorder (BD). As time to full BD onset decreases, symptoms of mania and depression seem to increase gradually in strength and prevalence. The specificity of prodromal symptoms and signs appears to be low. Not every person who develops BD experiences a prolonged initial prodrome to the full illness. Current data on the mean duration of the prodrome are contradictory, ranging from 1.8 to 7.3 years. No qualitative studies were found.
Limitations: Because of the scarcity of data, studies that did not explicitly investigate bipolar prodrome were included when thematically relevant. The selected studies are methodologically diverse and the validity of some findings is questionable. Findings must be interpreted cautiously.
Conclusions: The initial prodrome of BD is characterized by dysregulation of mood and energy. Because of the apparently low specificity of prodromal symptoms and signs of BD, it is currently neither possible nor advisable to predict the development of BD based solely on early phenomenology. More well-designed in-depth studies, including qualitative ones, are needed to characterize the initial bipolar prodrome.
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