Mania is the mood of an abnormally elevated arousal energy level, or "a state of heightened overall activation with enhanced affective expression together with lability of affect." Although mania is often conceived as a “mirror image” to depression, the heightened mood can be either euphoric or irritable; indeed, as the mania worsens, irritability often becomes more pronounced and may eventuate in violence. Mania is a syndrome of multiple aetiologies. Although the vast majority of cases occur in the context of bipolar disorder, it is a key component of other psychiatric illnesses (e.g., schizoaffective disorder, bipolar type) and may occur secondary to numerous general medical conditions or as a side-effect to certain medications or substances of abuse.