Complex sentence: There must also be evidence that the panic or anxiety symptoms are a direct result of the use of the intoxicating substance, which for caffeine-induced anxiety disorder would be due to the consumption of caffeine.
Split into simpler sentences: There must also be evidence that the panic or anxiety symptoms are a direct result of the use of the intoxicating substance. In caffeine-induced anxiety disorder, such symptoms would be due to the consumption of caffeine.