How do drugs affect the brain?

Encyclopedia of Opinion

Question: How do drugs affect the brain?
Position‹3 of 3: Stimulants elevate alertness and mood
Argument‹2 of 2: Amphetamines affect mood and cognition

Emotional and cognitive effects occur when amphetamines stimulate the central nervous system.

The argument

Amphetamines cause behavioural changes by affecting neurotransmitters in the brain; specifically dopamine and norepinephrine, the main neurotransmitters involved in the brain's reward and executive function pathways. The increased release and accumulation of dopamine resulting from amphetamine use causes euphoric feelings and can affect sexual desire and cognitive and behavioral control. Elevated norepinephrine levels stimulate locomotion and motor control, giving amphetamines potential performance-enhancing effects that have been exploited by some athletes. Amphetamines are highly addictive and the psychological and neurological impacts of withdrawal can be extreme, including depression, anxiety, fatigue, and an overwhelming urge to consume more amphetamines. Long-term use of amphetamines alters dopamine receptors and can result in both cognitive and motor impairments.

Premises

[P1]Amphetamines change behaviour by raising levels of the neurotransmitters dopamine and norepinephrine in the brain's reward and executive-function pathways. [P2] The surge in dopamine produces euphoria and alters cognitive and behavioural control, while elevated norepinephrine stimulates locomotion and gives a performance-enhancing effect. [P3] These same mechanisms make amphetamines highly addictive, with severe withdrawal and long-term cognitive and motor impairments. [C] Therefore, because amphetamines affect mood and cognition through these neurotransmitter pathways, stimulants elevate alertness and mood.

Counter-arguments

A rebuttal is that the argument's own emphasis undercuts the position it supports. The euphoria and heightened alertness it describes are acute, dose-dependent effects; the same drug, in withdrawal or with chronic use, produces depression, anxiety, fatigue and cognitive impairment. So "elevate alertness and mood" characterises only one phase of amphetamine action, not its overall effect. Critics add that the premise's stress on addiction and lasting impairment cuts against the tidy claim that stimulants straightforwardly "elevate" mood and cognition, since the net effect over time can be the reverse of elevation.

Rejecting the premises

[Rejecting P2] The euphoria and stimulation are acute, dose-dependent effects; in withdrawal or chronic use the same drug produces depression, anxiety and cognitive impairment, so "elevate mood" describes only one phase. [Rejecting P3] The premise's own emphasis on addiction and long-term impairment cuts against the position that stimulants simply "elevate alertness and mood," since the net effect over time can be the reverse.