What physiological effect is commonly observed in a subject under the influence of a hallucinogen?

When a subject is under the influence of a hallucinogen, one of the commonly observed physiological effects is elevated body temperature. Hallucinogens, such as LSD or psilocybin, often stimulate the central nervous system, leading to an increase in metabolic rate. This heightened state can result in an increase in body temperature as the body's processes become more active.

Elevated body temperature is significant in understanding the physiological impact that hallucinogens can have on individuals. Other effects might include changes in perception and mood, alterations in thought processes, and various autonomic responses, which can indirectly influence body temperature regulation.

While constricted pupils, elevated cholesterol, and hypotension may be associated with other categories of drugs, they are not typical effects seen with hallucinogens. Constricted pupils are often linked to opioids, elevated cholesterol is not a direct result of hallucinogenic use, and hypotension may occur with depressants but not typically with hallucinogens. Thus, elevated body temperature stands out as the correct response for this question concerning the effects of hallucinogens.