The effects of hallucinogens are typically more unpredictable than those of other drugs because the class contains several different compounds, each of which has effects that can vary greatly from person to person. The range of effects depends on a variety of factors: the amount ingested; physiological factors such as the user’s weight and metabolism; the user's personality, mood, history of mental illness, and expectations; the setting of use; whether the user is alone or with other people; and whether the substance is ingested alone or in conjunction with other drugs or alcohol.