Can you will yourself to think a thought?
Do you tell your mind to think this particular thought now and that one three seconds later?
And even if you can tell your mind what to do, does it listen?
It is neither a "brain" disorder or "mental" illness or even "psych" affliction. These all are just words. And the words prescribed by some "Doctors" can not define who you are.
We are a soul. And until we reach a place where we belong we will be beset with this sickening soul sickness.
In English, "manushya" is often translated simply as "human" or "human being". The term is derived from the Sanskrit root "manu," which means "to think" or "to understand," and reflects the importance of intellect and consciousness in defining what it means to be human.
But some birds who are stuck in a comfortable and convenient cage think that flying is an illness (“Birds born in a cage think flying is an illness.” ― Alejandro Jodorowsky).