The Cantonese layman term of bipolar disorder, often referred to as 狂躁症, can be regarded as a misnomer, and has been replaced by a more descriptive term such as 雙相情緒症 as there has been growing number of research demonstrating that irritability is not the most distinctive feature in bipolar disorder. Instead, symptom such as increase in energy level is a more distinctive feature of bipolar disorder. Nonetheless, the notion that significant irritability equates bipolar disorder is still commonly held locally, not only among the general population but also among some non-psychiatric doctors. It is further consolidated by the fact that irritable mood is still a central diagnostic feature of mania or hypomania in DSM-5. This article offers a comprehensive and up-to-date review of the role of irritability in contemporary psychiatry, from theories to research evidence. The authors also performed a meta-analysis on the prediction of irritability to psychiatric disorders using longitudinal studies. Interestingly, no significant findings were reported with regards to the development of bipolar disorder. Instead, depression and anxiety disorder were predicted by irritability. This article invariably provided the readers with more insight into and the clinical implications of the role of irritability in psychiatric disorders.