Pathological emotional expression, generally due to neurological degeneration or other complications; may or may not be mood-congruent. In other words, the patient might sob uncontrollably in an only moderately sad situation (an excessive but mood-congruent reaction), or he or she might also cry when upset or angry (a mood-incongruent reaction). Labile affect is also known as pseudobulbar affect, emotional incontinence, or involuntary emotional expression disorder (IEED).
Example: In describing her marriage, a woman is sobbing bitterly one moment, then laughing wildly the next.
Grinnell, R. (2008). Labile Affect. Psych Central. Retrieved on May 27, 2015, from http://psychcentral.com/encyclopedia/2008/labile-affect/