Drug dependence is a complex disorder characterized by substantial changes in patient's behavior and daily life. Both physical and psychological dependence have been recognized as separate entities. Numerous symptoms may develop and the diagnosis mandates a thorough patient history that will determine which substance was used, a thorough physical examination, and toxicology.
The clinical presentation can somewhat vary depending on the drug used, but the persistent need for drug use despite potentially harmful consequences, inability to regulate the frequency of its consumption and prioritizing its consumption over all other activities are hallmarks of drug dependence . Two main types of dependence are recognized  :
It is important to note that both physical and psychological dependence may be encountered in patients, making additional criteria highly useful in defining the diagnosis. Symptoms such as craving, tolerance (necessity to use larger amounts over time), repeated attempts to quit or control drug use, as well as giving up daily life activities due to dependence can be reported. When three or more symptoms are reported within a 12-month period, the diagnosis can be confirmed based on clinical criteria  .
The diagnostic workup must start with a carefully obtained patient history, as only a few questions during the interview may reveal the cause of symptoms and the substance that caused dependence. Physicians must bear in mind that peak dependence rates are during adolescence - Alcohol and marijuana dependence most likely occurs around 17-18 years of age, whereas cocaine abuse peaks around 23-25 years. of age . What is worrisome is that more than 10% of cocaine, marijuana and alcohol users become dependent within the first 10 years of use . These findings further emphasize the importance of a meticulous patient history regarding prior substance use and additional questions that will identify whether diagnostic criteria for dependence can be met . More importantly, information from parents, close relatives or friends may be particularly helpful when there is a suspicion of drug dependence, as the patient may not always disclose such information. If the diagnosis is not confirmed, toxicology testing can be performed for marijuana, cocaine, opioids, amphetamines, phencyclidine, benzodiazepines, barbiturates, and alcohol . Urine is tested most commonly, while blood, saliva, sweat or hair samples can be used as well .