Which of the following is NOT a symptom of cannabis overdose?

In the context of cannabis use, cannabis overdose is often associated with several symptoms that can affect both mental and physical states. Increased heart rate is a well-documented effect of cannabis, particularly in the case of high doses or individuals who may be more sensitive to its effects. Therefore, it cannot be considered a symptom of an overdose but rather a common physiological response to cannabis consumption.

On the other hand, insomnia, hyperactivity, and decreased activity are effects that can vary widely depending on the individual's body chemistry, tolerance, and the amount consumed. Insomnia may occur as a result of overstimulation or anxiety, while hyperactivity may arise in some cases where an individual's reaction to cannabis is more stimulating. Decreased activity is often a response to sedation, which can happen, especially with certain strains or when too much of the substance is ingested.

Thus, identifying increased heart rate as a symptom of cannabis consumption aligns with its pharmacological effects, making it the correct answer to distinguish it from the other options which can be seen more as symptoms related to an overdose scenario.