A 23-year-old male university
student is brought in to casualty by his flatmates. He says that he can hear
people talking about him over the radio.
He feels there is a plot against
him and that the people in charge of the radio station are trying to turn his
friends against him. At times he can hear voices in his head and he also feels
that these people take control of his actions at times.
His friends are concerned about his behaviour and ask you whether drug or
alcohol abuse could play a part in the aetiology of his condition.
You reply that the agent that can be considered a risk factor for development
of this condition is: