PTSD, is it caused by a blow to the head?

PTSD is not physical. It is a psychological (mental) condition caused by a traumatic (shocking) experience or set of experiences, such as sexual assault, being in battle, being attacked by violent criminals, seeing or being involved in an accident or disaster, that sort of thing. So if your friend was attacked or had a fall, that could cause PTSD. It's not the blow, it's the experience.

Contrex is correct.

Post-traumatic stress disorder is a psychological diagnosis.

Traditionally, to receive a PTSD diagnosis, a person must have had an experience which caused them to fear for their life. It was not an easy diagnosis to get.

An injury might have occurred at the same time as the incident which led to the diagnosis of PTSD, but the injury itself would not lead to the diagnosis.

Maybe you are thinking of a "closed head injury" which is caused by a blow to the head. It can cause psychological difficulties, too.

Hi! PTSD that is Post Traumatic Stress Disorder is caused when a person experiences or met with traumatic events like any event that has causes shock, some sort of assault, any emotional shock, any event from past, death and many more .

Post traumatic stress disorder is psychiatric disorder that can occur after you have been pass through a traumatic event like natural disasters , sexual or physical health problem and terrorist attacks.

Anyone who has had a very bad head injury is more prone to PTSD, early onset of Senile Dementia and a host of other mental illnesses .

You don't even need to suffer physical harm to have PTSD. As the name implies, it is distressed occurring after a traumatic experience. Let's say you survive a tornado unscathed. You can still have stress afterward.

It is PTSD when the stress felt afterward is prolonged. Most people bounce back and have resilience, but some never stop reliving the experience. By the way, constantly reliving the experience is a symptom. Survivors guilt can be another symptom. If your neighbors properties or lives were destroyed but you were fine, you may have some guilt afterward.
Can a traumatic injury also lead to PTSD? Yes. But, it is not the only cause. A lot of it has to do with the person's disposition before the event. Those who are pessimistic, feel helplessness, or less psychologically resilient are much more likely to get it.
The right help and resiliency tools can bring someone out of it a lot of the time.

I think the condition which can be caused by a blow to the head is called mtbi (minor traumatic brain injury) but I might be wrong. I am not a doctor.

your friend is an idiot.

Oh look at you, making new friends........