Psychiatrymiddle twist
A 19-year-old man is brought to the emergency department by police after being found shouting at parked cars. He is guarded, gives his name and little else, and denies using any drugs. His clothes are dirty and he is unkempt. There are no needle marks. He is afebrile, oriented to time and place, and attends to questions without difficulty. Physical and neurological examination is normal. His flatmate has followed the ambulance in and is waiting outside. Which one of the following will contribute most to establishing the diagnosis?