Which substance can lead to anxiety and tremors as side effects?

Amphetamines are stimulant drugs that can significantly influence the central nervous system, leading to elevated levels of energy and alertness. However, their stimulating effects can also result in undesirable side effects, including anxiety and tremors. When amphetamines increase the release of neurotransmitters like dopamine and norepinephrine, they can lead to heightened arousal and agitation. Consequently, users may experience anxiety and physical symptoms such as tremors as a response to the overstimulation.

While other substances listed can also cause various psychological or physical effects, their mechanisms and side effects differ. For instance, marijuana is generally associated more with relaxation, and while it can lead to anxiety in some individuals, it is not primarily known for inducing tremors. Alcohol can cause anxiety symptoms particularly associated with withdrawal rather than immediate use, and PCP can cause dissociative effects and delirium. However, amphetamines are directly linked to the stimulation of the nervous system that can precipitate the specific side effects mentioned in the question.