Is anosognosia a delusion, a negative symptom, or a cognitive deficit?

Anosognosia is the lack of awareness of a disabling physical or mental illness. The term was coined by Joseph Babinski in 1914 following his observations that patients with left-side paralysis due to right hemisphere stroke do not recognize their hemiplegia and strongly deny that there is anything physically wrong with their body, or that they need treatment or rehabilitation.

Psychiatrists have long observed anosognosia in patients with acute psychoses such as schizophrenia or mania who vehemently deny that there is anything wrong with them, despite experiencing hallucinations, delusions, and/or bizarre behavior. They adamantly refuse medical care and often have to be involuntarily hospitalized to receive urgently needed medications they don’t believe they need.

So is anosognosia in schizophrenia a fixed false belief (delusion), a negative symptom, or a cognitive deficit? Arguments can be made for any of those 3 options, but the evidence suggests that anosognosia is a disorder of consciousness, a “meta-cognitive” deficit, or, as I referred to it in a previous publication, the loss of self-proprioception.¹

Anosognosia in neurologic brain disorders

Although right hemispheric stroke is the most common disease state associated with anosognosia,² other neurologic disorders can be associated with anosognosia, including Anton’s syndrome of cortical blindness,³ traumatic brain injury,⁴ Wernicke’s aphasia,⁵ mild cognitive impairment,⁶ and Alzheimer’s disease.⁷ In addition to anosognosia, those disorders can be accompanied by indifference to the deficit, which is referred to as “anosodiaphoria.”

The neuroanatomy of anosognosia generally implicates right hemisphere deficits, especially the frontal cortex, the right parietal lobe, the temporoparietal cortex, and the thalamus. It can be conceptualized as a disturbance of “body schema” because all motor and sensory functions of the body have a “representation” in brain structure.

Anosognosia in psychiatric brain disorders

Although schizophrenia is most frequently associated with anosognosia, other psychiatric disorders also exhibit this absence of insight. They include delusional disorder,⁸ bipolar disorder,⁹ intellectual disability,¹⁰ and personality disorders.¹¹ In all those psychiatric disorders, there is a lack of self-reflection (metacognition). At the neuroanatomical level, most studies have focused on schizophrenia, and abnormalities have been described in the frontal and parietal regions. Significant pathology in the inferior parietal lobe has been identified in schizophrenia.¹² However, the right insula, which is connected to multiple neural circuits,¹³ appears to be intimately associated with anosognosia when impaired. The insula also regulates interoception and a “sense of self.”¹⁴ The loss of cortical gray matter in schizophrenia is most pronounced in the insula bilaterally. Another neurologic mechanism associated with anosognosia in schizophrenia is the default mode network (DMN). The DMN, which usually is overactive at rest and is deactivated during a focused activity, is involved in both insight and social cognition.¹⁵

Measurement of anosognosia

Several rating scales are used to measure the severity of anosognosia and the loss of insight. They include:

• The Insight and Treatment Attitude Questionnaire¹⁶
• The Scale to Assess Unawareness of Mental Disorder¹⁷
• The Beck Cognitive Insight Scale,¹⁸ the only self-administered scale that measures a patient’s ability to evaluate their psychiatric beliefs and possibly modify them
• The Positive and Negative Syndrome Scale,¹⁹ which is the gold standard for measuring the overall severity of schizophrenia, has only 1 item related to insight within the 16-item General Subscale (G12: Lack of judgement and insight).

Continue to: Consequences of anosognosia...