Which of the following describes general mental illness?

General mental illness is primarily characterized by its impact on a person's thoughts, emotions, and behaviors. This means that individuals with mental illnesses may experience alterations in their thinking patterns, may exhibit unusual behaviors, and might struggle with emotional regulation. Unlike conditions that solely affect physical health, mental illnesses involve complex interactions among psychological, biological, and social factors.

The other options do not adequately describe general mental illness. While substance addiction can be linked to mental health issues, it is a specific category rather than a broad description of mental illness. A high IQ is unrelated to mental illness and does not provide insight into mental health conditions. Hence, the most appropriate and encompassing description of general mental illness relates to its effects on thoughts and behaviors.