As a result of drug tolerance, some users of amphetamine would take large doses to experience a "high". From this, these users would develop symptoms of paranoia (auditory hallucinations, bizarre motor behavior, etc), which closely resembled schizophrenic symptoms.

Not only that, but amphetamine worsens symptoms of schizophrenia. Amphetamine is found to promote the release of dopamine and prolong the action of the released transmitter by blocking reuptake.

Drug Abuse as Support of the Dopamine Hypothesis of Antipsychotic Drugs

A process in which the body shows an enhanced response to a given drug after repeated doses

Bowdoin College

A condition in which, with repeated exposure to a drug, an individual becomes less responsive to a constant dose. 
 
- Metabolic tolerance 
- Functional tolerance 
- Behavioral Tolerance
- Cross-tolerance 
- Withdrawal symptoms
- Sensitization 


Drug tolerance

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

The form of drug tolerance that arises when repeated exposure to the drug causes the metabolic machinery of the body to become more efficient at clearing the drug.

Metabolic tolerance

Decreased responding to a drug after repeated exposures, generally as a consequence of up- or down- regulation of receptors. 

Functional tolerance

A condition in which the development of tolerance for one drug causes and individual to develop tolerance for another drug. 

Cross tolerance

An uncomfortable symptom that arises when a person stops taking a drug that he or she has used frequently, especially at high doses.

Withdrawal symptoms

Drug sensitization

The body learns to rapidly down-regulate the function of a specific neurotransmitter when environmental cues for the drug are present. This decreases the effect of the drug on the body. Overdoses are more likely to occur when environmental cues are not present, since body does not down-regulate the receptors for this drug. 

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