Withdrawal symptoms can vary significantly among individuals, but there are some commonalities, such as depression, anxiety and craving, and if extreme can help drive the individual to continue the drug despite significant harm — the very definition of addiction — or even to suicide.

However, addiction is to be carefully distinguished from physical dependence. Addiction is a psychological compulsion to use a drug despite harm that often persists long after all physical withdrawal symptoms have abated. On the other hand, the mere presence of even profound physical dependence does not necessarily denote addiction, e.g., in a patient using large doses of copious to control chronic pain under medical supervision.

TYPES OF ADDICTION

   Physical Dependency

Physical dependence on a substance is defined by the appearance of characteristic withdrawal symptoms when the substance is suddenly discontinued. Opiates, Amphetamines, benzodiazepines, barbiturates, alcohol and nicotine induce physical dependence. On the other hand, some categories of substances share this property and are still not considered addictive: cortisone, beta-blockers and most antidepressants are examples. So, while physical dependency can be a major factor in the psychology of addiction and most often becomes a primary motivator in the continuation of an addiction, the initial primary attribution of an addictive substance is usually its ability to induce pleasure, although with continued use the goal is not so much to induce pleasure as it is to relieve the anxiety caused by the absence of a given addictive substance, causing it to become used compulsively. An example of this is nicotine; A cigarette can be described as pleasurable, but is in fact fulfilling the physical addiction of the user, and therefore, is achieving pleasurable feelings relative to his/her previous state of physical withdrawal. Further, the physical dependency of the nicotine addict on the substance itself becomes an overwhelming factor in the continuation of use.

The speed with which a given individual becomes addicted to various substances varies with the substance, the frequency of use, the means of ingestion, the intensity of pleasure or euphoria, and the individual's genetic and psychological susceptibility. Some people may exhibit alcoholic tendencies from the moment of first intoxication, while most people can drink socially without ever becoming addicted. Opioid dependent individuals have different responses to even low doses of opioids than the majority of people, although this may be due to a variety of other factors, as opioid use heavily stimulates pleasure-inducing neurotransmitters in the brain. Nonetheless, because of these variations, in addition to the adoption and twin studies that have been well replicated, much of the medical community is satisfied that addiction is in part genetically moderated. That is, one's genetic makeup may regulate how susceptible one is to a substance and how easily one may become psychologically attached to a pleasurable routine.

   Psychological Dependency

Psychological dependency is a dependency of the mind, and leads to psychological withdrawal symptoms (such as cravings, irritability, insomnia, depression, anorexia, etc). Addiction can in theory be derived from any rewarding behavior, and is believed to be strongly associated with the system of the brain's reward system (as in the case of cocaine and amphetamines). Some claim that it is a habitual means to avoid undesired activity, but typically it is only so to a clinical level in individuals who have emotional, social, or psychological dysfunctions (psychological addiction is defined as such), replacing normal positive stimuli not otherwise attained.

It is considered possible to be both psychologically and physically dependent at the same time. Some doctors, and especially scientists in related fields, make little or no distinction between the two types of addiction, since the result, substance abuse, is the same, and in terms of scientific as opposed to magical thinking, the "psychological" dependence is entirely due to physical effects of the drug on the brain.

Psychological dependence does not have to be limited only to substances; even activities and behavioral patterns can be considered addictions, if they become uncontrollable, e.g. gambling, Internet addiction, computer addiction, sexual addiction / pornography addiction, reading, eating, self-harm, vandalism, drug addiction or work addiction.