Can someone explain what a mental disorder is to me?
I've tried looking around to understand what a `mental disorder` actually means, and I find the concept to be difficult to grasp.
In particular, according to medlineplus.gov: "Mental disorders (or mental illnesses) are conditions that affect your thinking, feeling, mood, and behavior."
However, I find this definition to be very confusing. Most mental illnesses are diagnosed based on behavioural patterns. For example, if a person has narcissistic tendencies or behaves narcissistically, he/she suffers from the narcissistic personality disorder. That behavior is then caused by this condition.
What about if a drug addict goes to rehab and suffers from withdrawal symptoms, which affects his/her "thinking, feeling, mood, and behavior," has the rehab brought about a mental disorder? If it's not a mental disorder, is it not a mental disorder because we know what caused it? Vice-versa, if we didn't know what caused it, would it be a mental disorder then?
What about homosexuality? Homosexuality and transsexuality used to be mental disorders, but now they decided that they're not. Why's that? Just because we think that the behavior is now acceptable?
Is a mental disorder just descriptive of behavior? If so, why do we say someone suffers from a narcissistic personality disorder, instead of saying that the person has narcissistic tendencies? To absolve them of responsibility?