Lack of awareness of illness, poor insight or ‘denial’ are regarded as fundamental problems in neurology and psychiatry. The ‘object’ of the awareness differs in different conditions. For example a stroke patient may deny their hemiplegia (anosognosia) – a deficit which is visible and objective; a person with Alzheimer’s disease may be unaware of memory problems – which though measurable, are not readily apparent to the observer. Finally, a schizophrenic patient with hallucinations may or may not accept that the ‘voices’ that they alone hear are part of a mental illness. In neuropsychiatry the discrepancy between the patients’ and the relatives’ ratings provide a useful measure of ‘insight’.
In psychiatry, it is more common to use a clinician rating and to consider separate domains. It has been have suggested that insight in psychosis concerns 3 domains: (1) awareness of mental disorder, (2) ability to re-label psychotic phenomena as pathological, (3) compliance with treatment. This last dimension is obviously important clinically. One question for research is whether these different types of lack of awareness share a common aetiology. Within schizophrenia, insight appears to be correlated with general intellectual functioning. However, this does not explain why many patients are able to detect signs of mental disorder in another person but not themselves. There is some evidence that additional executive or ‘frontal lobe’ deficits contribute to lack of insight. More recently neuroimaging studies using MRI and voxel-based morphometric techniques have shown areas of reduced grey matter density that correlate with loss of various components of insight. Hence insight in psychiatry and neurology has come together thanks to advances in brain imaging.
Pijnenborg GH, van Donkersgoed RJ, David AS, & Aleman A (2013). Changes in insight during treatment for psychotic disorders: a meta-analysis. Schizophrenia research, 144 (1-3), 109-17 PMID: 23305612