Correlates and long-term consequences of poor insight in patients with schizophrenia. A systematic review

Between 50 and 80% of the patients diagnosed with schizophrenia have been shown to be partially or totally lacking insight into the presence of their mental disorder. Although a causal chain connecting poor insight with poor treatment adherence and thus with poorer outcome and functioning is straight forward, numerous studies investigating correlates and long-term impact of insight have provided differing results. In addition, higher levels of insight in schizophrenia have been associated with depression and hopelessness, but the causal direction of the relationship is unclear and the data are inconclusive. The current study provides a critical review of 88 studies on the assessment of insight and its impact on symptoms and functioning. Studies published by June 2006 were selected using a keyword search for English peer-reviewed articles in the databases PsycINFO and MEDLINE. The majority of studies support the assumption that insight is associated with adherence during treatment phase, but the association with long-term adherence remains unclear. Insight correlates with better long-term functioning, but this might be explained by its association with symptoms. There is a positive cross-sectional and longitudinal relationship between insight and depression, but the underlying processes need further clarification. In the concluding discussion, the problems relating to definition and study designs are considered responsible for many of the inconclusive findings. Suggestions for further research are derived.