Which of the following is associated with cannabis use and includes red or irritated eyes?

The association of cannabis use with bloodshot eyes is well-documented. When a person uses cannabis, the active compounds, particularly THC, cause the blood vessels in the eyes to expand, leading to a noticeable reddening. This physiological effect results in what is commonly referred to as "bloodshot eyes."

This symptom occurs because THC lowers blood pressure and causes the dilation of blood vessels, which is why many people notice their eyes becoming red or irritated after consumption. Bloodshot eyes are a recognizable and often stereotyped sign of cannabis use, making this choice the most fitting answer to the question regarding the effects associated with cannabis.

While piloerection refers to the hair standing on end, and difficulty in speech is often related to other factors or substances, relaxed inhibitions can result from various psychoactive substances, not exclusively cannabis. Thus, bloodshot eyes stand out as a clear and specific indicator linked to cannabis use.