The common symptoms of drug dependence include tolerance, withdrawal, and inability to stop using. Addicts spend a lot of time figuring out how to obtain drugs, and they may also act criminally to get the substances they need because they are driven by an overwhelming and a seemingly unconquerable sense that they cannot survive without them. Moreover, substance dependence has common outward signs that may be, but are not always, noticed by the addict or other people in his life.
As people become substance-dependent, tolerance is established. This means that former amounts used are not enough to produce the same effects. The addict often takes greater amounts of the drug in an effort to obtain a satisfactory feeling.
In drug dependence, tolerance is directly linked to withdrawal. Since the body is more used to the addictive substance and needs it more regularly, it begins to produce withdrawal symptoms quickly, which can include agitation, nervousness, emotional changes, and nausea/vomiting. These feelings make it very difficult to stop using, and most addicts return to the drug used in order to stop withdrawal effects. In a sense, they’ve transitioned from the original purpose of the drug, i.e., sedation, relaxation, or pain relief, to using it to avoid or stop withdrawal.
The symptoms of tolerance and withdrawal partly explain why it is so difficult to arrest the cycle of drug dependence. Addicts may feel like there is no way to stop without incurring very negative physical symptoms. Emotional dependence on the drug is frequently established, too, and people may believe they have no choice but to keep using. Those with substance addiction may often entertain the notion of quitting, but many can’t stop without help because tolerance, withdrawal, and emotional dependence are a triple-threat barrier.
Living with drug dependence frequently means spending a lot of time each day figuring out how to get or maintain a drug supply. People may commit crimes to get drugs, whether they are illegal or are only available by prescription. They might doctor shop, a practice where multiple doctors are seen to obtain new prescriptions, and they could steal or commit acts of prostitution to pay for illegal drugs. Even when substances are available easily, like alcohol, their use reduces normal cautionary behavior, resulting in acts like driving under the influence.
Relatives or friends can notice some signs of substance dependence. These include frequent episodes of altered, "drugged," behavior. A disinterest in previously important activities or dropping all friends in favor of one or two new acquaintances is also suspicious. Quick emotional changes and sudden failure in work or school may be symptomatic of drug dependence, too, as is missing money or property, which may signify the individual’s attempts to obtain needed substances.