The pathological use of substances falls into 2 categories. Substance dependence presence of at least 3 of the following. The person develops tolerance, indicated by larger doses of the substance being needed to produce the desired effect or the effects of the drug becoming markedly less if the usual mount is taken. Withdrawal symptoms (negative physical and psychological effects when they stop taking it) The person uses more of the substance or uses it for a longer time than intended. The person recognizes excessive use of the substance, he/she may tried to reduce usage but has been unable to do so. Much of the person"s time is spent in efforts to obtain the substance or recover from its effects. Substance use continues despite psychological or physiological problems caused or exacerbated by the drug. The person gives up or cuts back participation in many activities.