Insight - in mental health terms - is being aware that one's behaviour and/or feelings are not healthy or usual. In relation to obsessive-compulsive disorder (OCD) insight can be viewed as occuring on a continuum ranging from full awareness of the absurdity of obsessions and compulsions to a total lack of any such awareness. An Italian study of insight among 75 patients with OCD found that poor or absent insight was associated with higher perceived expressed emotion*, a higher severity of OCD symptoms, higher familial perceived criticism and more compulsions and depressive symptoms.
De Berardis, Domenico ... [et al] - Insight and perceived expressed emotion among adult outpatients with obsessive-compulsive disorder Journal of Psychiatric Practice May 2008, 14(3), 137-145
*http://en.wikipedia.org/wiki/Expressed_emotion for an explanation of expressed emotion