Growing evidence suggests that patients with bipolar disorder (BD) are impaired in their ability to process non-verbal emotion, although few comprehensive reviews of the behavioural literature exist, and there has been little consideration of methodological issues that may account for discrepant empirical findings. This review examines the behavioural facial, prosodic and multimodal processing literature in BD and discusses methodological issues in the context of this evidence.
Major computer databases including Google Scholar and PsychINFO were consulted to conduct a comprehensive review of quantitative behavioural differences in the emotion-processing literature in BD. Articles were accepted only if the target population sample met criteria for a DSM-III, DSM-IV or ICD-10 diagnosis, and they contained a healthy control group.
The current literature suggests that facial emotion processing is impaired, and there is preliminary evidence for some behavioural impairment in the processing of emotional prosody.
The specificity or generalisability of impairments in facial emotion processing and the effects of mood state are unclear. Similarly, the lack of clarity around the impact of auditory processes on emotional prosody processing warrants a comprehensive examination of the auditory profile in BD.