What illness affects the mind and reduces a persons ability to function?

The correct answer is mental illness. Mental illnesses are a diverse group of conditions that affect a person's thinking, emotions, behavior, and overall mental well-being. They can range from mild to severe and can significantly impair a person's ability to function in daily life, including their ability to work, go to school, or maintain relationships. Some examples of mental illnesses include depression, anxiety disorders, bipolar disorder, schizophrenia, and personality disorders. It's important to seek help from a mental health professional if you or someone you know is struggling with mental health issues.