Delusional parasitosis

The clip is the opening scene of A Scanner Darkly based on the novel by Phillip K Dick. In the film most of the characters take a drug called substance D. This may or may not be amphetamine (speed) or could even be a reference to dopamine. The writer of the book did take large amounts of amphetamine and experienced significant mental health problems during his lifetime. In the clip one of the characters appears to be infested with bugs he calls aphids. This is delusional parasitosis a type of psychosis that can be caused by amphetamine and cocaine abuse.

Amphetamine use increases dopamine levels and can lead to a form of psychosis that is very similar to paranoid schizophrenia. This is strong evidence that some types of schizophrenia may be caused by problems in the regulation or action of dopamine on the dopamine systems in the brain. This is known as the dopamine hypothesis.

Link to an article in 'The Psychologist' magazine on neuropsychology and psychosis in Phillip K Dick's A Scanner Darkly