POLICE ASSOCIATION OF NOVA SCOTIA 129 (continued...) People may also commit crimes in order to make money to buy drugs, and drug problems are frequent among criminal offenders. Tolerance Tolerance means that, over time and with regular use, a person who uses drugs needs more and more of a drug to get the same effect. Tolerance increases the physical health risks of any drug simply because it can result in increased drug use over time. Tolerance also increases the risk of dangerous or fatal overdose, for two reasons. First, the body does not necessarily develop tolerance to all the effects of the drug to the same extent. Long-term use of barbiturates, for example, causes a person to become tolerant to the mood-altering effect of barbiturates, but less so to their depressant effect on respiration. When this happens, the dose required to achieve the mood-altering effect may be dangerously close to the lethal dose and death can result from respiratory failure. Second, if a person has not taken the drug in a long time, the expected tolerance may actually have decreased. So, after a long period of abstinence, the size of the dose the person had previously become accustomed to may actually be enough to cause a life threatening or fatal overdose. As people age, physiological changes may mean they need less of a drug to get the same effect. This result may be compounded if their liver or kidneys have been damaged by chronic disease. Physical Dependence Physical dependence occurs when a person's body becomes so accustomed to a particular drug that it can only function normally if the drug is present. If people who use drugs drastically reduce their level of use or stop using the drug abruptly, they may experience a variety of signs and symptoms ranging from mild discomfort to seizures. These e ffects, some of which can be fatal, are collectively referred to as "withdrawal." Withdrawal symptoms are often opposite to the effects produced by taking the drug, e.g. when a person stops using a stimulant drug such as cocaine they may become depressed, need to sleep a lot, and have increased appetite when they awaken. To avoid the discomfort of withdrawal, the person who uses drugs may start to use again or feel unable to stop using the drug. Not all drugs produce physical dependence, but they may still be abused because the person who uses drugs becomes psychologically dependent on the drug's effects. Psychological Dependence Psychological dependence exists when a drug is so central to a person's thoughts, emotions and activities that it is extremely difficult to stop using it, or even stop thinking about it. A strong desire or craving to use a drug may be triggered by internal or external cues such as the end of a meal for smokers or seeing injection equipment for people who inject drugs. Like physical dependence, psychological dependence is a cause of continued drug use. An individual may be both psychologically and physically dependent on a drug. Overdose An overdose of any drug is a dose that can cause serious and sudden physical or mental damage. An overdose may or may not be fatal, depending on the drug and the amount taken. Dangerous overdoses are more likely to occur in people who have developed a tolerance for some effects of a drug more than others, those who return to drug use after a long period of abstinence, or those who use drugs illegally and have no way of knowing the exact potency of what they are buying. Sudden increases in the purity of some (...continued)
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