Well in a sense PTSD isn't exactly 'abnormal' I mean it involves normal body processes...what is abnormal about it is it can put your body in defense mode where its not necessary causing one to be in a state of over-stress which can contribute to other health problems. From what I understand there are changes in the brain and body that cause the over-active stress response. Also though not everyone who experiences trauma develops PTSD, no one experiences it and is un-effected but not everyone ends up with PTSD...so while its not an abnormal response to trauma(it does make sense such an event could f*** someone up) It still does end up being a Disorder because of how debilitating it is. Also I'd say my brain before PTSD was different....so for me it is now abnormal compared to what was 'normal' for me. Before it was normal for me to be able to concentrate really well on studying/researching/reading and all that stuff after that my concentration was destroyed essentially..but that is just one example of one abnormality I noticed.

But its the same with lots of mental disorders, like Depression feeling down and such isn't abnormal...but depression can take it to an extreme to where you constantly feel that way even if there isn't a situational reason.

All mental disorders are essentially normal human behavior/reactions that happen to such an extent it can be debilitating for that individual. And I would agree that a holistic approach when dealing with a mental illness or disorder is important as the brain and body are not separate entities.