How do drugs affect the brain?

Cannabis causes euphoria and alters perception

Question: How do drugs affect the brain?
Position‹2 of 3›: Depressants slow brain and nervous system function
Argument‹4 of 4: Cannabis causes euphoria and alters perception

One of the most popular recreational drugs, cannabis, affects the brain via cannabinoid compounds.

The argument

The active compounds within cannabis are called cannabinoids. These compounds interact with and activate specific cannabinoid receptor molecules throughout the body, including in the brain and nervous system. Cannabinoids also increase the activity of dopamine in the brain's mesolimbic pathway, also known as the reward pathway, which can affect motivation, desire, and pleasure responses after consumption. Prolonged use of cannabis can result in cognitive impairment and worsen the symptoms of mental illness as tolerance to the effects of cannabinoids increases.

Premises

[P1]The cannabinoids in cannabis activate receptor molecules throughout the brain and nervous system. [P2] They raise dopamine in the brain's reward pathway, affecting motivation, desire and pleasure. [P3] Prolonged use causes cognitive impairment and can worsen mental illness as tolerance grows. [C] Therefore, cannabis acts on the central nervous system to cause euphoria and alter perception.

Counter-arguments

A counter notes that cannabis is not straightforwardly a depressant. Pharmacologists typically classify it separately as a cannabinoid, and its effects are mixed — depressant, stimulant and hallucinogenic — depending on dose, strain and individual. Raising dopamine in the brain's reward pathway is characteristic of rewarding and stimulant drugs generally, not specifically of depressants, so the mechanism the argument describes does not by itself locate cannabis among substances that 'slow' the nervous system. Placing it under 'depressants' is therefore a contested categorisation rather than a settled one, and the euphoria and altered perception it cites are as consistent with stimulant or hallucinogenic classification.

Rejecting the premises

[Rejecting P2] Increasing dopamine in the reward pathway is common to many drug classes, including stimulants, so it does not specifically identify cannabis as a depressant. [Rejecting C] Pharmacologists usually class cannabis as its own cannabinoid category with mixed depressant, stimulant and hallucinogenic effects, so slotting it solely under 'depressants' is a contested simplification.