Addiction is the continued problematic repetition of a behaviour, physiologically and/or psychologically. Classic hallmarks of addiction include impaired control over substance use or behavior, preoccupation with an activity, using despite consequences, and denying there is a problem. Physical dependence occurs when your body has to adjust to the substance by incorporating the substance into its 'normal' functioning. This can lead to tolerance and withdrawal.
Tolerance is when your body continually adapts to a substance and requires increasingly larger amounts to achieve the same effects. Withdrawal refers to the physical and psychological symptoms experienced when reducing or discontinuing a substance the body has become dependent on.
In order to experience the symptoms of withdrawal, one must have first developed a physical or mental dependence. The route of administration, whether intravenous, intramuscular, oral or otherwise, can also play a role in determining the severity of withdrawal symptoms. Symptoms of withdrawal may include, but are not limited to: anxiety, irritability, intense cravings, nausea, hallucinations, headaches, cold sweats and tremors - these will differ depending on substance from which one is withdrawing. Depending on the length of time a drug takes to leave the bloodstream (elimination half-life), withdrawal symptoms can appear within a few hours to several days after discontinuation and may also occur in the form of cravings. 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 opioids to control chronic pain under medical supervision.
It is important to note that one can become addicted to a substance regardless of whether it is considered physically addictive or not. There are many substances which do not initially form physical addiction, but are psychologically addictive and will form physical addiction with continued use. Also note that the addictive potential of a chemical is not necessarily correlated to its legal status or general attitude within society (alcohol, cannabis). Great care and respect should be given in the use of any chemical to ensure that one does not fall into an abuse pattern. It is important to understand that a person with an addiction may or may not become physically dependent. Signs of physical dependency may appear dissimilarly from one person to the next.
An addictive behaviour is any activity or behaviour that becomes the major focus of a person's life, resulting in a physical, mental, and/or social withdrawal from their normal day to day obligations. There are different types of addiction and virtually any activity or substance has the potential to become addictive. Drugs, alcohol, and nicotine are examples of substance addictions, whereas behavioural addictions may include gambling, sexual activity, Internet, food related behaviours, shopping, work, or exercise. Compulsions and addictions are intertwined. Addiction involves the compulsion to take an addictive substance (such as alcohol or heroin) or to carry out an addictive behaviour. Compulsive behaviours are repetitious and are performed in an effort to reduce or control tension resulting from inner feelings often generated by anxiety, stress or insecurity. Compulsive behaviours are often ritualistic but typically do not escalate and the compulsions are not carried out in a secretive and deceitful manner.