Which is a symptom of hallucinogen use?

The correct answer highlights that severe mood disorders can be a symptom of hallucinogen use. Hallucinogens, such as LSD or psilocybin, affect a person's perception of reality and may lead to profound changes in mood. Users can experience intense feelings that can swing erratically, leading to severe anxiety, paranoia, or depression. This emotional volatility is a direct result of how these substances alter neurotransmitter activity in the brain, particularly around serotonin pathways, which can significantly impact mood regulation.

On the other hand, excessive sleepiness, increased physical coordination, and heightened awareness of surroundings do not accurately characterize the effects of hallucinogens. In fact, hallucinogens are more likely to cause wakefulness and an altered state of consciousness, rather than any increased physical coordination or the simplistic awareness one might expect. Their use is generally associated with vivid hallucinations and changes in sensory perception, rather than the mentioned symptoms.