Insight can be defined not only in terms of people's understanding of their illness, but also in terms of understanding how the illness affects individuals' interactions with the world. The term 'insight' encompasses a complex concept which should not be considered as an isolated symptom which is present or absent. Instead, it may be more appropriate to think of insight as a continuum of thinking and feeling, affected by numerous internal and external variables. Different psychiatric disorders involve different mechanisms in the process of impairment of insight; this may influence the ways in which insight should be assessed in clinical practice.