Regarding the general adaptation syndrome (GAS), the first signs of psychosomatic disorder generally appear in what stage?
I'm a little unsure on the phrasing of the question, but I believe this is what you are looking for.
The first stage is Alarm Reaction which is the immediate reaction to a stressor. This is where us as humans exhibit a "fight or flight" response, which prepares the body for physical activity. Interestingly enough during the initial response it can decrease the effectiveness of the immune system, thus making a human more susceptible to illness in this stage.