A condition that prevents some people’s brains from recognizing and accepting that they are ill. It is especially common in some people with such severe mental illnesses such as bipolar disorder and schizophrenia.
A disorder in the brain’s frontal lobe, anosognosia is the biggest reason that roughly half of people diagnosed with schizophrenia and, to a lesser extent, those diagnosed with bipolar disorder, are unwilling to take their prescribed medications, or more fundamentally, to seek treatment. Anosognosia prevents them from correctly perceiving objects, distances, other people, others’ facial features, situations, etc.
Theirs is not a conscious denial of treatment, but an inability to recognize their medical need or real-time, actual circumstances. That’s true, even as many people with agnosia often maintain cognitive abilities — the capacity to process information/knowledge thoughtfully, rationally, reasonably — in many other areas.