Which of the following is considered a minor condition rather than a major mental illness?

Capgras syndrome is classified as a minor condition because it is a specific type of delusional disorder, where the affected individual harbors the belief that someone they know has been replaced by an imposter. This condition may arise in the context of a larger psychiatric or neurological condition, such as dementia or schizophrenia, but on its own, it does not carry the same level of pervasive impact on one’s overall functioning or quality of life typically associated with major mental illnesses.

In contrast, schizophrenia, bipolar disorder, and major depressive disorder are well-established major mental illnesses that can lead to significant impairment in daily functioning, and often require intensive treatment and management. These conditions involve more severe symptoms that affect various aspects of a person's life, including emotional regulation, perception of reality, and overall thought processes, thereby categorizing them as major mental illnesses.