In Europe, the rate of problem gambling is typically 0.5 to 3 percent. The "British Gambling Prevalence Survey 2007", conducted by the United Kingdom Gambling Commission, found approximately 0.6 percent of the adult population had problem gambling issues—the same percentage as in 1999. The highest prevalence of problem gambling was found among those who participated in spread betting (14.7%), fixed odds betting terminals (11.2%) and betting exchanges (9.8%). In Norway, a December 2007 study showed the amount of present problem gamblers was 0.7 percent.

Most research has focused on adult population or on college students, but little is known about epidemiology of behavioral addictions in adolescence. A study conducted by Villella "et al" looked at a group of students and the prevalence of various addictions. His results showed exercise addiction was the second most prevalent, after compulsive buying.

High risk groups that appear to be addicted to exercise include athletes in sports encouraging thinness or appearance standards, young and middle-age women, and young men.

A gambler who does not receive treatment for pathological gambling when in his or her desperation phase may contemplate suicide. Problem gambling is often associated with increased suicidal ideation and attempts compared to the general population.

Early onset of problem gambling increases the lifetime risk of suicide. However, gambling-related suicide attempts are usually made by older people with problem gambling. Both comorbid substance use and comorbid mental disorders increase the risk of suicide in people with problem gambling. A 2010 Australian hospital study found that 17% of suicidal patients admitted to the Alfred Hospital's emergency department were problem gamblers. In the United States, a report by the National Council on Problem Gambling showed approximately one in five pathological gamblers attempt suicide. The council also said that suicide rates among pathological gamblers were higher than any other addictive disorder.

Specific genes predispose people to drug addiction—it's one of the behavioral disorders most strongly corrolated with genetic makeup—but environmental factors, especially trauma and mistreatment in childhood, also correlate strongly with addiction. . Examples such as physical or sexual abuse, and unpredictable expectations and behavior of parents, increase a person's risk for developing addiction.

Individuals with exercise addiction may put exercise above family and friends, work, injuries, and other social activities. If not identified and treated, an exercise addiction may lead to a significant decline in one's health.

Exercise provides benefits for our bodies, but to some people, the benefits turn into health hazards. To some exercisers, rigorous physical activity becomes the central aspect of their lives. When a preoccupation with exercise has become routine, a person is considered addicted to exercise or exercise dependent. A study done shows why people may become addicted to exercise, especially running. One of the reasons people become addicted to exercise is because of the release of mood-enhancing chemicals known as endorphins. Endorphins increase the sensation of pleasure, which is why people feel good about themselves after they exercise. Endorphins are also responsible for the "runner's high." Recent studies have lent weight to the alternative theory that the addictive appeal of exercise is due to the production of endocannabinoids, naturally produced chemicals that bind to the brain's CB1 receptor, rather than to endorphin production. Those who suffer from exercise addiction will go through physical and emotional withdrawals in the absence of exercise, just like a person who is addicted to other substances, such as drugs or alcohol. Although in many cases, running is a better alternative than substance abuse. The findings in this study conclude that there is a link between negative addiction to running and interpersonal difficulties, which is common in other addictive behaviors as well.

Another growing area is social media addiction. Psychology researchers surveyed 253 undergraduate students at the University of Albany and found that not only is social media (particularly Facebook) itself potentially addictive, those who use it may also be at greater risk for substance abuse.

Internet addiction disorder, more commonly called problematic Internet use (PIU), refers to excessive Internet use that interferes with daily life.

A conceptual model of PIU has been developed based on primary data collected from addiction researchers, psychologists, and health providers as well as older adolescents themselves. That study identified seven concepts, or clusters, that make up PIU using a concept mapping approach. These seven clusters are: psychosocial risk factors; physical impairment; emotional impairment; social and functional impairment; risky Internet use; impulsive Internet use; and Internet use dependence. The last three constructs have not been previously identified. Risky Internet use are behaviors that increase risks of adverse consequences. It is not just the amount of time spent on the Internet that puts an adolescent at risk; how the time is spent is also an important consideration. The impulsive use construct describes an inability to maintain balance or control of internet use in relation to everyday life. Finally, the dependent use construct reflects the more severe symptoms that are typically associated with addictions, such as withdrawal symptoms. Thus, internet addiction may represent a severe form of PIU.

Other research also stresses the fact that the Internet addiction disorder is not a unidimensional but a multidimensional construct. Various facets of Internet use must be differentiated because of their differential predictors, mechanisms and consequences. Online activities which, if done in person, would normally be considered troublesome, such as compulsive gambling, or shopping, are sometimes called "net compulsions".

Diagnostic models do not currently include the criteria necessary to identify behaviors as addictions in a clinical setting. Behavioral addictions has been proposed as a new class in DSM-5, but the only category included is gambling addiction. Internet gaming addiction is included in the appendix as a condition for further study.

Behavioral addictions, which are sometimes referred to as impulse control disorders, are increasingly recognized as treatable forms of addiction.

The type of excessive behaviors identified as being addictive include gambling, food, sexual intercourse, use of pornography, use of computers, playing video games, use of the internet, exercise, and shopping.

Researching addiction to food, for example, a 2009 Scripps Research Institute study found evidence that the same molecular mechanisms correlated with human drug addiction also exist in compulsive overeating in obese rats. The dopamine D receptor studied is associated with vulnerability to drug addiction in humans. It was found downregulated in obese rats exposed to a high fat diet, and further reductions of the receptor increased compulsive eating. The D receptor responds to dopamine, a central neurotransmitter released in anticipation of rewarding, satiating experiences such as those involving food, sex or psychoactive drugs.

On August 15, 2011 the American Society of Addiction Medicine (ASAM) issued a public statement defining all addiction in terms of brain changes. "Addiction is a primary, chronic disease of brain reward, motivation, memory and related circuitry."

The following excerpts are taken from the organization's FAQs: The new ASAM definition makes a departure from equating addiction with just substance dependence, by describing how addiction is also related to behaviors that are rewarding. This is the first time that ASAM has taken an official position that addiction is not solely "substance dependence." This definition says that addiction is about functioning and brain circuitry and how the structure and function of the brains of persons with addiction differ from the structure and function of the brains of persons who do not have addiction. It talks about reward circuitry in the brain and related circuitry, but the emphasis is not on the external rewards that act on the reward system. Food and sexual behaviors and gambling behaviors can be associated with the "pathological pursuit of rewards" described in this new definition of addiction.

We all have the brain reward circuitry that makes food and sex rewarding. In fact, this is a survival mechanism. In a healthy brain, these rewards have feedback mechanisms for satiety or 'enough.' In someone with addiction, the circuitry becomes dysfunctional such that the message to the individual becomes ‘more’, which leads to the pathological pursuit of rewards and/or relief through the use of substances and behaviors. So, anyone who has addiction is vulnerable to food and sex addiction.

Since ASAM released its statement, and shortly before its release, additional new studies have come out on Internet addiction. They reveal the same fundamental brain changes seen in other addicts of drugs. Another 2011 study found that the risk of Internet addiction in men was about three times more than women. Researchers noted, Internet addiction is a psychosocial disorder and its characteristics are as follows: tolerance, withdrawal symptoms, affective disorders, and problems in social relations. Internet usage creates psychological, social, school and/or work difficulties in a person's life. Eighteen percent of study participants were considered to be pathological Internet users, whose excessive use of the Internet was causing academic, social, and interpersonal problems. Excessive Internet use may create a heightened level of psychological arousal, resulting in little sleep, failure to eat for long periods, and limited physical activity, possibly leading to the user experiencing physical and mental health problems such as depression, OCD, low family relationships and anxiety.

As demonstrated by the chart below, numerous studies have examined factors which mediate substance abuse or dependence. In these examples, the predictor variables lead to the mediator which in turn leads to the outcome, which is always substance abuse or dependence. For example, research has found that being raised in a single-parent home can lead to increased exposure to stress and that increased exposure to stress, not being raised in a single-parent home, leads to substance abuse or dependence. The following are some, but by no means all, of the possible mediators of substance abuse.

As demonstrated by the chart below, numerous studies have examined factors which moderate substance abuse or dependence. In these examples, the moderator variable impacts the level to which the strength of the relationship varies between a given predictor variable and the outcome of substance abuse or dependence. For example, there is a significant relationship between psychobehavioral risk factors, such as tolerance of deviance, rebelliousness, achievement, perceived drug risk, familism, family church attendance and other factors, and substance abuse and dependence. That relationship is moderated by familism which means that the strength of the relationship is increased or decreased based on the level of familism present in a given individual.

Examples of mediators and moderators can be found in several empirical studies. For example, Pilgrim et al.’s hypothesized mediation model posited that school success and time spent with friends mediated the relationship between parental involvement and risk-taking behavior with substance use (2006). More specifically, the relationship between parental involvement and risk-taking behavior is explained via the interaction with third variables, school success and time spent with friends. In this example, increased parental involvement led to increased school success and decreased time with friends, both of which were associated with decreased drug use. Another example of mediation involved risk-taking behaviors. As risk-taking behaviors increased, school success decreased and time with friends increased, both of which were associated with increased drug use.

A second example of a mediating variable is depression. In a study by Lo and Cheng (2007), depression was found to mediate the relationship between childhood maltreatment and subsequent substance abuse in adulthood. In other words, childhood physical abuse is associated with increased depression, which in turn, in associated with increased drug and alcohol use in young adulthood. More specifically, depression helps to explain how childhood abuse is related to subsequent substance abuse in young adulthood.

A third example of a mediating variable is an increase of externalizing symptoms. King and Chassin (2008) conducted research examining the relationship between stressful life events and drug dependence in young adulthood. Their findings identified problematic externalizing behavior on subsequent substance dependency. In other words, stressful life events are associated with externalizing symptoms, such as aggression or hostility, which can lead to peer alienation or acceptance by socially deviant peers, which could lead to increased drug use. The relationship between stressful life events and subsequent drug dependence however exists via the presence of the mediation effects of externalizing behaviors.

An example of a moderating variable is level of cognitive distortion. An individual with high levels of cognitive distortion might react adversely to potentially innocuous events, and may have increased difficulty reacting to them in an adaptive manner (Shoal & Giancola, 2005). In their study, Shoal and Giancola investigated the moderating effects of cognitive distortion on adolescent substance use. Individuals with low levels of cognitive distortion may be more apt to choose more adaptive methods of coping with social problems, thereby potentially reducing the risk of drug use. Individuals with high levels of cognitive distortions, because of their increased misperceptions and misattributions, are at increased risk for social difficulties. Individuals may be more likely to react aggressively or inappropriately, potentially alienating themselves from their peers, thereby putting them at greater risk for delinquent behaviors, including substance use and abuse. In this study, social problems are a significant risk factor for drug use when moderated by high levels of cognitive distortions.

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.

Kimberly Young indicates that previous research links internet/computer addiction with existing mental health issues, most notably depression. She states that computer addiction has significant effects socially such as low self-esteem, psychologically and occupationally which led many subjects to academic failure.

According to a Korean study on internet/computer addiction, pathological use of the internet results in negative life impacts such as job loss, marriage breakdown, financial debt, and academic failure. 70% of internet users in Korea are reported to play online games, 18% of which are diagnosed as game addicts which relates to internet/computer addiction. The authors of the article conducted a study using Kimberly Young's questionnaire. The study showed that the majority of those who met the requirements of internet/computer addiction suffered from interpersonal difficulties and stress and that those addicted to online games specifically responded that they hoped to avoid reality.

An addictive behavior is a behavior, or a stimulus related to a behavior (e.g., sex or food), that is both rewarding and reinforcing, and is associated with the development of an addiction. Addictions involving addictive behaviors are normally referred to as behavioral addictions.

Compulsive behavior is defined as performing an act persistently and repetitively without it necessarily leading to an actual reward or pleasure. Compulsive behaviors could be an attempt to make obsessions go away. The act is usually a small, restricted and repetitive behavior, yet not disturbing in a pathological way. Compulsive behaviors are a need to reduce apprehension caused by internal feelings a person wants to abstain from or control. A major cause of the compulsive behaviors is said to be obsessive–compulsive disorder (OCD). "The main idea of compulsive behavior is that the likely excessive activity is not connected to the purpose to which it appears directed." Furthermore, there are many different types of compulsive behaviors including, shopping, hoarding, eating, gambling, trichotillomania and picking skin, checking, counting, washing, sex, and more. Also, there are cultural examples of compulsive behavior.

Not only are there significant health risks associated with compulsive hoarding, but scientists are also trying to pinpoint how significant the interference is with occupational and social functioning in a hoarder's daily life. In a pool of compulsive hoarders, 42% found their behavior problematic to the 63% of their family and friends who saw the behavior as problematic. The findings suggest that individuals who hoard may exhibit impaired sensitivity to their own and others’ emotions, and conversely, relate the world around them by forming attachments to possessions rather than to people. Lower emotional intelligence among hoarding patients may also impact their ability to discard and organize their possessions. With such detrimental characteristics, comprehensive research has been performed to find a cure. Although this is ongoing research, most investigations have found that only a third of patients who hoard show an adequate response to these medications and therapeutic interventions.

With the modifications to the DSM, insurance coverage for treatments will change as well as special education programs.

Some evidence based on brain lesion case studies also suggests that the anterior ventromedial prefrontal and cingulate cortices may be involved in abnormal hoarding behaviors, but sufferers of such injuries display less purposeful behavior than other individuals who hoard compulsively, thus making the involvement of these brain structures unclear. Other neuropsychological factors that have been found to be associated with individuals exhibiting hoarding behaviors include slower and more variable reaction times, increased impulsivity, and decreased spatial attention. A study comparing neural activity in hoarders, people with OCD, and a control group when deciding to throw possessions away found that when hoarders were trying to decide to throw away their own possessions, they had lower activity in the anterior cingulate cortex and insula regions of the brain. The study suggested this lower activity was related to "problems in identifying the emotional significance of a stimulus, generating appropriate emotional response, or regulating affective state during decision making." Hoarders had normal levels of activity in those regions when making decisions about possessions that did not belong to them.

Compulsive checking can include compulsively checking items such as locks, switches, and appliances. This type of compulsion usually deals with checking whether harm to oneself or others is possible. Usually, most checking behaviors occur due to wanting to keep others and the individual safe.

People that suffer from compulsive counting tend to have a specific number that is of importance in the situation they are in. When a number is considered significant, the individual has a desire to do the behavior such as wiping ones face off the number of times that is significant. Compulsive counting can include instances of counting things such as steps, items, behaviors, and mental counting.

Compulsive repeating is characterized by doing the same activity multiple times over. These activities can include re-reading a part of a book multiple times, re-writing something multiple times, repeating routine activities, or saying the same phrase over and over.

Compulsive washing is usually found in individuals that have a fear of contamination. People that have compulsive hand washing behaviors wash their hands repeatedly throughout the day. These hand washings can be ritualized and follow a pattern. People that have problems with compulsive hand washing tend to have problems with chapped or red hands due to the excessive amount of washing done each day.

Psychological dependency on a substance is defined by the appearance of emotional-motivational withdrawal symptoms (e.g., anxiety, irritability, anhedonia, depressed mood, restlessness, etc.) when the substance is suddenly discontinued. Psychological dependence is not unique to substances; for example, separation anxiety occurs in young children when they lack exposure to individuals to whom they're emotionally attached.

Excessive computer use may result in, or occur with:

- Lack of face to face social interaction

- Computer vision syndrome

According to a systematic review from 2014, prevalence rates of sexual addiction and related sexual disorders ranges from 3% to 6%.

Television addiction is a proposed addiction model associated with maladaptive or compulsive behavior associated with watching television programming. The most recent medical review on this model concluded that pathological television watching behavior may constitute a true behavioral addiction, but indicated that much more research on this topic is needed to demonstrate this. The compulsion can be extremely difficult to control in many cases. The television addiction model has parallels to other forms of behavioral addiction, such as addiction to drugs or gambling, which are also forms of compulsive behavior.

Television addiction is not a diagnosable condition of DSM-IV.

Internet sex addiction, also known as cybersex addiction, has been proposed as a sexual addiction characterized by virtual Internet sexual activity that causes serious negative consequences to one's physical, mental, social, and/or financial well-being. It may also be considered a subset of the theorized Internet addiction disorder. Internet sex addiction manifests various behaviours: reading erotic stories; viewing, downloading or trading online pornography; online activity in adult fantasy chat rooms; cybersex relationships; masturbation while engaged in online activity that contributes to one's sexual arousal; the search for offline sexual partners and information about sexual activity.

Comorbidity of addictive disorders and other psychiatric disorders, i.e., dual disorders, is very common and a large body of literature has accumulated demonstrating that mental disorders are strongly associated with substance use disorders. The 2011 USA National Survey on Drug Use and Health found that 17.5% of adults with a mental illness had a co-occurring substance use disorder; this works out to 7.98 million people. Estimates of co-occurring disorders in Canada are even higher, with an estimated 40-60% of adults with a severe and persistent mental illness experiencing a substance use disorder in their lifetime.

A study by Kessler et al. in the United States attempting to assess the prevalence of dual diagnosis found that 47% of clients with schizophrenia had a substance misuse disorder at some time in their life, and the chances of developing a substance misuse disorder was significantly higher among patients suffering from a psychotic illness than in those without a psychotic illness.

Another study looked at the extent of substance misuse in a group of 187 chronically mentally ill patients living in the community. According to the clinician's ratings, around a third of the sample used alcohol, street drugs, or both during the six months before evaluation.

Further UK studies have shown slightly more moderate rates of substance misuse among mentally ill individuals. One study found that individuals suffering from schizophrenia showed just a 7% prevalence of problematic drug use in the year prior to being interviewed and 21% reported problematic use some time before that.

Wright and colleagues identified individuals with psychotic illnesses who had been in contact with services in the London borough of Croydon over the previous 6 months. Cases of alcohol or substance misuse and dependence were identified through standardized interviews with clients and keyworkers. Results showed that prevalence rates of dual diagnosis were 33% for the use of any substance, 20% for alcohol misuse only and 5% for drug misuse only. A lifetime history of any illicit drug use was observed in 35% of the sample.

The dependence potential of a drug varies from substance to substance, and from individual to individual. Dose, frequency, pharmacokinetics of a particular substance, route of administration, and time are critical factors for developing a drug dependence.

An article in "The Lancet" compared the harm and dependence liability of 20 drugs, using a scale from zero to three for physical dependence, psychological dependence, and pleasure to create a mean score for dependence. Selected results can be seen in the chart below.