The DSM definition of addiction can be boiled down to compulsive use of a substance (or engagement in an activity) despite ongoing negative consequences. The medical community makes a distinction between physical dependence (characterized by symptoms of physical withdrawal symptoms, like tremors and sweating) and psychological dependence (emotional-motivational withdrawal symptoms). Physical dependence is simply needing a substance to function. Humans are all physically dependent upon oxygen, food and water. A drug can cause physical dependence and not psychological dependence (for example, some blood pressure medications, which can produce fatal withdrawal symptoms if not tapered) and some can cause psychological dependence without physical dependence (the withdrawal symptoms associated with cocaine are all psychological, there is no associated vomiting or diarrhea as there is with opiate withdrawal).

There are several different screening tools that have been validated for use with adolescents such as the CRAFFT and adults such as the CAGE.

Signs and symptoms include:

- Drug seeking behavior

- Multiple prescriptions from different providers

- Increased use over time

- Opioid cravings

- Multiple medical complications from drug use (HIV/AIDS, hospitalizations, abscesses)

- Legal or social ramifications secondary to drug use

- Withdrawal symptoms

Physical dependence on a substance is defined by the appearance of characteristic physical withdrawal symptoms when the substance is suddenly discontinued. Opiates, 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.

Some substances induce physical dependence or physiological tolerance - but not addiction — for example many laxatives, which are not psychoactive; nasal decongestants, which can cause rebound congestion if used for more than a few days in a row; and some antidepressants, most notably venlafaxine, paroxetine and sertraline, as they have quite short half-lives, so stopping them abruptly causes a more rapid change in the neurotransmitter balance in the brain than many other antidepressants. Many non-addictive prescription drugs should not be suddenly stopped, so a doctor should be consulted before abruptly discontinuing them.

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 attached to a pleasurable routine.

Eating disorders are complicated pathological mental illnesses and thus are not the same as addictions described in this article. Eating disorders, which some argue are not addictions at all, are driven by a multitude of factors, most of which are highly different from the factors behind addictions described in this article. It has been reported, however, that patients with eating disorders can successfully be treated with the same non-pharmacological protocols used in patients with chemical addiction disorders.

Gambling is another potentially addictive behavior with some biological overlap. Conversely gambling urges have emerged with the administration of Mirapex (pramipexole), a dopamine agonist.

The obsolete term physical addiction is deprecated, because of its connotations. In modern pain management with opioids physical dependence is nearly universal. High-quality, long-term studies are needed to better delineate the risks and benefits of chronic opiate use.

Cannabis use is associated with comorbid mental health problems, such as mood and anxiety disorders, and discontinuing cannabis use is difficult for some users. Psychiatric comorbidities are often present in dependent cannabis users including a range of personality disorders.

Signs and symptoms of opioid intoxication include:

- Decreased perception of pain

- Euphoria

- Confusion

- Desire to sleep

- Nausea

- Constipation

- Miosis

Cannabis withdrawal symptoms can occur in one half of patients in treatment for cannabis use disorders. These symptoms include dysphoria (anxiety, irritability, depression, restlessness), disturbed sleep, gastrointestinal symptoms, and decreased appetite. Most symptoms begin during the first week of abstinence and resolve after a few weeks.

According to the National Cannabis Prevention and Information Centre in Australia, a sign of cannabis dependence is that an individual spends noticeably more time than the average recreational user recovering from the use of or obtaining cannabis. For some, using cannabis becomes a substantial and disruptive part of an individual's life and he or she may exhibit difficulties in meeting personal obligations or participating in important life activities, preferring to use cannabis instead. People who are cannabis dependent have the inability to stop or decrease using cannabis on their own.

Substance dependence also known as drug dependence is an adaptive state that develops from repeated drug administration, and which results in withdrawal upon cessation of drug use. A "drug addiction", a distinct concept from substance dependence, is defined as compulsive, out-of-control drug use, despite negative consequences. An "addictive drug" is a drug which is both rewarding and reinforcing. ΔFosB, a gene transcription factor, is now known to be a critical component and common factor in the development of virtually all forms of behavioral addiction and drug addictions, but not dependence.

Within the framework of the 4th edition of the "Diagnostic and Statistical Manual of Mental Disorders" ("DSM-IV"), substance dependence is redefined as a drug addiction, and can be diagnosed without the occurrence of a withdrawal syndrome. It is now described accordingly: "When an individual persists in use of alcohol or other drugs despite problems related to use of the substance, substance dependence may be diagnosed. Compulsive and repetitive use may result in tolerance to the effect of the drug and withdrawal symptoms when use is reduced or stopped. This, along with Substance Abuse are considered Substance Use Disorders."

Withdrawal is the body's reaction to abstaining from a substance upon which a person has developed a dependence syndrome. When dependence has developed, cessation of substance use produces an unpleasant state, which promotes continued drug use through negative reinforcement; i.e., the drug is used to escape or avoid re-entering the associated withdrawal state. The withdrawal state may include physical-somatic symptoms (physical dependence), emotional-motivational symptoms (psychological dependence), or both. Chemical and hormonal imbalances may arise if the substance is not introduced. Psychological stress may also result if the substance is not re-introduced.

Infants also suffer from substance withdrawal, known as Neonnatal Abstinence Syndrome (NAS) which has severe and life-threatening effects on growing fetus. Addiction to drugs and alcohol in expecting mothers does not only cause NAS but also an array of other issues which can continually affect the infant throughout his/her lifetime. The type of drug which was abused during the months of pregnancy has many different effects on the child which can affect the infant in many ways throughout his/her life.

The signs and symptoms of benzodiazepine dependence include feeling unable to cope without the drug, unsuccessful

attempts to cut down or stop benzodiazepine use, tolerance to the effects of benzodiazepines, and withdrawal symptoms when not taking the drug. Some withdrawal symptoms that may appear include anxiety, depressed mood, depersonalisation, derealisation, sleep disturbance, hypersensitivity to touch and pain, tremor, shakiness, muscular aches, pains, twitches, and headache. Benzodiazepine dependence and withdrawal have been associated with suicide and self-harming behaviors, especially in young people. The Department of Health substance misuse guidelines recommend monitoring for mood disorder in those dependent on or withdrawing from benzodiazepines.

Benzodiazepine dependence is a frequent complication for those prescribed for or using for longer than four weeks, with physical dependence and withdrawal symptoms being the most common problem, but also occasionally drug-seeking behavior. Withdrawal symptoms include anxiety, perceptual disturbances, distortion of all the senses, dysphoria, and, in rare cases, psychosis and epileptic seizures.

Addiction is defined by Webster Dictionary as a "compulsive need for and use of a habit-forming substance characterized by tolerance and by well-defined physiological symptoms upon withdrawal; broadly: persistent compulsive use of a substance known by the user to be harmful".

Problematic Internet use is also called compulsive Internet use (CIU), Internet overuse, problematic computer use, or pathological computer use (PCU), problematic Internet use (PIU), or Internet addiction disorder (IAD)). Another commonly associated pathology is video game addiction, or Internet gaming disorder (IGD).

Nicotine dependence develops over time as a person continues to smoke. The risk for the development of dependence and how long it takes to become dependent differs from person to person; there is not a clear consensus on how long it takes for dependence to develop.

Nicotine dependence results in daily, heavy usage of cigarettes and produces withdrawal symptoms such as urges to smoke, negative moods, and difficulty concentrating, when the person stops smoking. These withdrawal symptoms are so unpleasant that smokers very frequently return to smoking. However, while it is known what nicotine dependence does—permits heavy smoking and causes severe withdrawal symptoms and relapse back to smoking—it is hard to measure nicotine dependence apart from these consequences.

Nicotine dependence has been classified as a chronic, relapsing disease. In other words, it is a long-term disorder that may have periods of relapse and remission that require repeated intervention, similar to other chronic conditions such as diabetes or hypertension. This perspective reinforces the idea that nicotine dependence is not a bad habit but an actual disease that requires ongoing treatment.

Benzodiazepine dependence is the condition resulting from repeated use of benzodiazepine drugs. It can include both a physical dependence as well as a psychological dependence and is typified by a withdrawal syndrome upon a fall in blood plasma levels of benzodiazepines, e.g., during dose reduction or abrupt withdrawal.

Internet addiction disorder is not listed in the latest DSM manual (DSM-5, 2013), which is commonly used by psychiatrists. Gambling disorder is the only behavioural (non-substance related) addiction included in DSM-5. However Internet gaming disorder is listed in Section III, Conditions for Further Study, as a disorder requiring further study.

Jerald J. Block, M.D. has argued that Internet addiction should be included as a disorder in the DSM-5. However, Block observed that diagnosis was complicated because 86% of study subjects showing symptoms also exhibited other diagnosable mental health disorders.

Impulsivity is characterized by actions based on sudden desires, whims, or inclinations rather than careful thought. Individuals with substance abuse have higher levels of impulsivity, and individuals who use multiple drugs tend to be more impulsive. A number of studies using the Iowa gambling task as a measure for impulsive behavior found that drug using populations made more risky choices compared to healthy controls. There is a hypothesis that the loss of impulse control may be due to impaired inhibitory control resulting from drug induced changes that take place in the frontal cortex. The neurodevelopmental and hormonal changes that happen during adolescence may modulate impulse control that could possibly lead to the experimentation with drugs and may lead to the road of addiction. Impulsivity is thought to be a facet trait in the neuroticism personality domain (overindulgence/negative urgency) which is prospectively associated with the development of substance abuse.

Psychological dependence is a form of dependence that involves emotional–motivational withdrawal symptoms (e.g., a state of unease or dissatisfaction, a reduced capacity to experience pleasure, or anxiety) upon cessation of drug use or engagement in certain behaviors. Physical and psychological dependence are sometimes classified as a facet or component of addiction, such as in the DSM-IV-TR; however, some drugs which produce dependence syndromes do not produce addiction, and vice versa, in humans. Addiction and psychological dependence are both mediated through reinforcement, a form of operant conditioning, but are associated with different forms of reinforcement. Addiction is a compulsion for rewarding stimuli that is mediated through positive reinforcement. Psychological dependence, which is mediated through negative reinforcement, involves a desire to use a drug or perform a behavior to avoid the unpleasant withdrawal syndrome that results from cessation of exposure to it.

Psychological dependence develops through consistent and frequent exposure to a stimulus. Behaviors which can produce observable psychological withdrawal symptoms (i.e., cause psychological dependence) include physical exercise, shopping, sex and self-stimulation using pornography, and eating food with high sugar or fat content, among others. Behavioral therapy is typically employed to help individuals overcome psychological dependence upon drugs or maladaptive behaviors that produce psychological dependence.

Research by governments in Australia led to a universal definition for that country which appears to be the only research-based definition not to use diagnostic criteria: "Problem gambling is characterized by many difficulties in limiting money and/or time spent on gambling which leads to adverse consequences for the gambler, others, or for the community." The University of Maryland Medical Center defines pathological gambling as "being unable to resist impulses to gamble, which can lead to severe personal or social consequences".

Most other definitions of problem gambling can usually be simplified to any gambling that causes harm to the gambler or someone else in any way; however, these definitions are usually coupled with descriptions of the type of harm or the use of diagnostic criteria. The "DSM-V" has since reclassified pathological gambling as "gambling disorder" and has listed the disorder under substance-related and addictive disorders rather than impulse-control disorders. This is due to the symptomatology of the disorder resembling an addiction not dissimilar to that of substance-abuse. There are both environmental and genetic factors that can influence on gambler and cause some type of addiction. In order to be diagnosed, an individual must have at least four of the following symptoms in a 12-month period:

- Needs to gamble with increasing amounts of money in order to achieve the desired excitement

- Is restless or irritable when attempting to cut down or stop gambling

- Has made repeated unsuccessful efforts to control, cut back, or stop gambling

- Is often preoccupied with gambling (e.g., having persistent thoughts of reliving past gambling experiences, handicapping or planning the next venture, thinking of ways to get money with which to gamble)

- Often gambles when feeling distressed (e.g., helpless, guilty, anxious, depressed)

- After losing money gambling, often returns another day to get even ("chasing" one's losses)

- Lies to conceal the extent of involvement with gambling

- Has jeopardized or lost a significant relationship, job, education or career opportunity because of gambling

- Relies on others to provide money to relieve desperate financial situations caused by gambling

Depending on the actual compound, drug abuse including alcohol may lead to health problems, social problems, morbidity, injuries, unprotected sex, violence, deaths, motor vehicle accidents, homicides, suicides, physical dependence or psychological addiction.

There is a high rate of suicide in alcoholics and other drug abusers. The reasons believed to cause the increased risk of suicide include the long-term abuse of alcohol and other drugs causing physiological distortion of brain chemistry as well as the social isolation. Another factor is the acute intoxicating effects of the drugs may make suicide more likely to occur. Suicide is also very common in adolescent alcohol abusers, with 1 in 4 suicides in adolescents being related to alcohol abuse. In the USA approximately 30% of suicides are related to alcohol abuse. Alcohol abuse is also associated with increased risks of committing criminal offences including child abuse, domestic violence, rapes, burglaries and assaults.

Drug abuse, including alcohol and prescription drugs, can induce symptomatology which resembles mental illness. This can occur both in the intoxicated state and also during the withdrawal state. In some cases these substance induced psychiatric disorders can persist long after detoxification, such as prolonged psychosis or depression after amphetamine or cocaine abuse. A protracted withdrawal syndrome can also occur with symptoms persisting for months after cessation of use. Benzodiazepines are the most notable drug for inducing prolonged withdrawal effects with symptoms sometimes persisting for years after cessation of use. Abuse of hallucinogens can trigger delusional and other psychotic phenomena long after cessation of use.

Cannabis may trigger panic attacks during intoxication and with continued use, it may cause a state similar to dysthymia. Researchers have found that daily cannabis use and the use of high-potency cannabis are independently associated with a higher chance of developing schizophrenia and other psychotic disorders.

Severe anxiety and depression are commonly induced by sustained alcohol abuse, which in most cases abates with prolonged abstinence. Even sustained moderate alcohol use may increase anxiety and depression levels in some individuals. In most cases these drug induced psychiatric disorders fade away with prolonged abstinence.

Nicotine dependence, or tobacco use disorder, is a state of dependence upon nicotine. There are different ways of measuring nicotine dependence. Some nicotine dependence assessments focus on key physical dependence outcomes like the development of tolerance which allows people to smoke heavily. Other assessments ask about psychosocial outcomes or underlying mechanisms of dependence. These different assessments either characterize dependence as a continuous construct or use cut-offs to diagnose whether or not a person is dependent.

Nicotine dependence is especially a concern among some populations such as those with co-occurring mental illness. There are evidence-based nicotine dependence treatments that include both medication and psychosocial interventions that can significantly increase a smoker’s chances of quitting successfully.

Problem gambling (or ludomania, but usually referred to as "gambling addiction" or "compulsive gambling") is an urge to gamble continuously despite harmful negative consequences or a desire to stop. Problem gambling is often defined by whether harm is experienced by the gambler or others, rather than by the gambler's behaviour. Severe problem gambling may be diagnosed as clinical pathological gambling if the gambler meets certain criteria. Pathological gambling is a common disorder that is associated with both social and family costs.

The "DSM-5" has re-classified the condition as an addictive disorder, with sufferers exhibiting many similarities to those who have substance addictions.

The term "gambling addiction" has long been used in the recovery movement. Pathological gambling was long considered by the American Psychiatric Association to be an impulse control disorder rather than an addiction. However, data suggest a closer relationship between pathological gambling and substance use disorders than exists between PG and obsessive-compulsive disorder, largely because the behaviors in problem gambling and most primary substance use disorders ("i.e.", those not resulting from a desire to "self-medicate" for another condition such as depression) seek to activate the brain's reward mechanisms while the behaviors characterizing obsessive-compulsive disorder are prompted by overactive and misplaced signals from the brain's fear mechanisms.

Problem gambling is an addictive behavior with a high comorbidity with alcohol problems. Comorbidity is the presence of one or more diseases or disorders co-occurring with each other. A common feature shared by people who suffer from gambling addiction is impulsivity.

Cocaine is a powerful stimulant known to make users feel energetic, happy, talkative, etc. In time, negative side effects include increased body temperature, irregular or rapid heart rate, high blood pressure, increased risk of heart attacks, strokes and even sudden death from cardiac arrest. Many habitual abusers develop a transient, manic-like condition similar to amphetamine psychosis and schizophrenia, whose symptoms include aggression, severe paranoia, restlessness, confusion and tactile hallucinations; which can include the feeling of insects under the skin (formication), also known as "coke bugs", during binges. Users of cocaine have also reported having thoughts of suicide, unusual weight loss, trouble maintaining relationships, and an unhealthy, pale appearance.

Barbiturate dependence develops with regular use of barbiturates. This in turn may lead to a need for increasing doses of the drug to get the original desired pharmacological or therapeutic effect. Barbiturate use can lead to both addiction and physical dependence, and as such they have a high potential for abuse. Management of barbiturate dependence involves considering the affected person's age, comorbidity and the pharmacological pathways of barbiturates. Psychological addiction to barbiturates can develop quickly. The GABA receptor, one of barbiturates' main sites of action, is thought to play a pivotal role in the development of tolerance to and dependence on barbiturates, as well as the euphoric "high" that results from their abuse. The mechanism by which barbiturate tolerance develops is believed to be different from that of ethanol or benzodiazepines, even though these drugs have been shown to exhibit cross-tolerance with each other. The management of a physical dependence on barbiturates is stabilisation on the long-acting barbiturate phenobarbital followed by a gradual titration down of dose. The slowly eliminated phenobarbital lessens the severity of the withdrawal syndrome and reduces the chances of serious barbiturate withdrawal effects such as seizures. Antipsychotics are not recommended for barbiturate withdrawal (or other CNS depressant withdrawal states) especially clozapine, olanzapine or low potency phenothiazines e.g. chlorpromazine as they lower the seizure threshold and can worsen withdrawal effects; if used extreme caution is required.

Some of the fundamental components of kleptomania include recurring intrusive thoughts, impotence to resist the compulsion to engage in stealing, and the release of pressure following the act. These symptoms suggest that kleptomania could be regarded as an obsessive-compulsive type of disorder.

People diagnosed with kleptomania often have other types of disorders involving mood, anxiety, eating, impulse control, and drug use. They also have great levels of stress, guilt, and remorse, and privacy issues accompanying the act of stealing. These signs are considered to either cause or intensify general comorbid disorders. The characteristics of the behaviors associated with stealing could result in other problems as well, which include social segregation and substance abuse. The many types of other disorders frequently occurring along with kleptomania usually make clinical diagnosis uncertain.

There is a difference between ordinary theft and kleptomania: "ordinary theft (whether planned or impulsive) is deliberate and is motivated by the usefulness of the object or its monetary worth," whereas with kleptomania, there "is the recurrent failure to resist impulses to steal items even though the items are not needed for personal use or for their monetary value."

Compulsions and addictions are intertwined and reward is one major distinction between an addiction and a compulsion (as it is experienced in obsessive-compulsive disorder). An addiction is, by definition, a form of compulsion, and both addictions and compulsions involve operant reinforcement; however, in addiction, the desire and motivation to use a substance or engage in a behavior arises because it is rewarding (i.e., the compulsions that occur in addiction develop through positive reinforcement). In contrast, someone who experiences a compulsion as part of obsessive-compulsive disorder may not perceive anything rewarding from acting on the compulsion. Often, it is a way of dealing with the obsessive part of the disorder, resulting in a feeling of relief (i.e., compulsions may also arise through negative reinforcement).

Deep brain stimulation to the nucleus accumbens, a region in the brain involved heavily in addiction and reinforcement learning, has proven to be an effective treatment of obsessive compulsive disorder.

Behavioral addiction is a form of addiction that involves a compulsion to engage in a rewarding non-drug-related behavior – sometimes called a natural reward – despite any negative consequences to the person's physical, mental, social or financial well-being. A gene transcription factor known as ΔFosB has been identified as a necessary common factor involved in both behavioral and drug addictions, which are associated with the same set of neural adaptations in the reward system.

Cocaine dependence is a psychological desire to use cocaine regularly. Cocaine overdose may result in cardiovascular and brain damage, such as: constricting blood vessels in the brain, causing strokes and constricting arteries in the heart; causing heart attacks.

The use of cocaine creates euphoria and high amounts of energy. If taken in large, unsafe doses, it is possible to cause mood swings, paranoia, insomnia, psychosis, high blood pressure, a fast heart rate, panic attacks, cognitive impairments and drastic changes in personality.

The symptoms of cocaine withdrawal (also known as "comedown or crash") range from moderate to severe: dysphoria, depression, anxiety, psychological and physical weakness, pain, and compulsive cravings.