Lack of insight into illness is a prevalent and distinguishing feature of schizophrenia, which has a complex history and has been given a variety of definitions. Currently, insight is measured and treated as a multidimensional phenomenon, because it is believed to result from psychological, neuropsychological and organic factors. Thus, schizophrenia patients may display dramatic disorders including demoralization, depression and a higher risk of suicide, all of which are directly or indirectly related to a lack of insight into their illness, and make the treatment difficult. To improve the treatment of people with schizophrenia, it is thus crucial to advance research on insight into their illness. Insight is studied in a variety of ways. Studies may focus on the relationship between insight and psychopathology, may view behavioral outcomes or look discretely at the cognitive dysfunction versus anatomy level of insight. All have merit but they are dispersed across a wide body of literature and rarely are the findings integrated and synthesized in a meaningful way. The aim of this study was to synthesize findings across the large body of literature dealing with insight, to highlight its multidimensional nature, measurement, neuropsychology and social impact in schizophrenia. The extensive literature on the cognitive consequences of lack of insight and the contribution of neuroimaging techniques to elucidating neurological etiology of insight deficits, is also reviewed.Key words: cognition impairment, conceptualization, insight, neuroanatomy, schizophrenia.A MONG PATIENTS WITH psychiatric disorders, patients with schizophrenia more often exhibit poor insight concerning their mental disorder. 1 The World Health Organization (WHO) International Pilot Study of Schizophrenia in different cultures found that 'lack of insight' was an almost invariable feature of acute and chronic schizophrenia. That study found that 50-80% of patients lack, either partially or totally, insight into their mental disorder.2 A rich literature indicated that unawareness of illness is associated with defects in cognitive functions such as attention, memory, language, executive functioning and social cognition. [3][4][5][6][7][8][9] Furthermore, poor insight in schizophrenia has been proposed to result in poor treatment compliance, 10,11 poor social and interpersonal functioning, 12,13 poor prognosis, and higher risk of relapse.14 Other studies reported that poor insight may increase the incidence of depression, hopelessness, low self-esteem [15][16][17][18][19] and more generally poor quality of life (QOL). 13,[20][21][22] Over the past decade there has been an increase in research on the conceptualization and assessment of insight, but the relationship between insight and neurocognitive impairment, severity of psychopathology or *Correspondence: Mounir Ouzir, PhD, Laboratory of Clinical Neuroscience and Mental Health, University Hassan II, Faculty of Medicine and Pharmacy, 19 Rue Tarik Ibnou Ziad, BP: 9154 Mers Sultan, 20000 Casablanca, M...