There is some evidence supporting the claim that excessive mobile phone use can cause or worsen health problems.

Germs are everywhere, and considering the number of times people interact with their cellphone under different circumstances and places, germs are very likely to transfer from one place to another. Research from the London School of Hygiene & Tropical Medicine at Queen Mary in 2011 indicated that one in six cell phones is contaminated with fecal matter. Under further inspection, some of the phones with the fecal matter were also harboring lethal bacteria such as "E. coli", which can result in fever, vomiting, and diarrhea.

According to the article "Mobile Phones and Nosocomial Infections," written by researchers at Mansoura University of Egypt, it states that the risk of transmitting the bacteria by the medical staff (who carry their cellphones during their shift) is much higher because cellphones act as a reservoir where the bacteria can thrive.

Cancer, specifically brain cancer, and its correlation with phone use, is under ongoing investigation. Many variables affect the likelihood of hosting cancerous cells, including how long and how frequently people use their phones. There has been no definitive evidence linking cancer and phone use if used moderately, but the International Agency for Research on Cancer of the World Health Organization said in 2011 that radio frequency is a possible human carcinogen, based on heavy usage increasing the risk of developing glioma tumors — a common benign tumor, a rare but deadly form of cancer. Although a relationship has not been fully established, research is continuing based on leads from changing patterns of mobile phone use over time and habits of phone users. Low level radio frequency radiation has also been confirmed as a promoter of tumors.

Minor acute immediate effects of radio frequency exposure have long been known such as Tinnitus or Microwave auditory effect which was discovered in 1962.

Studies show that users often associate using a mobile phone with headaches, impaired memory and concentration, fatigue, dizziness and disturbed sleep. These are all symptoms of radiation sickness. There are also concerns that some people may develop electrosensitivity or IEI-EMF from excessive exposure to electromagnetic fields.

Using a cell phone before bed can cause insomnia, according to a study by scientists from the Karolinska Institute and Uppsala University in Sweden and from Wayne State University in Michigan. The study showed that this is due to the radiation received by the user as stated, "The study indicates that during laboratory exposure to 884 MHz wireless signals, components of sleep believed to be important for recovery from daily wear and tear are adversely affected." Additional adverse health effects attributable to smartphone usage include a diminished quantity and quality of sleep due to an inhibited secretion of melatonin.

In 2014, 58% of World Health Organization states advised the general population to reduce radio frequency exposure below heating guidelines. The most common advice is to use hands-free kits (69%), to reduce call time (44%), use text messaging (36%), avoid calling with low signals (24%) or use phones with low specific absorption rate (SAR) (22%). In 2015 Taiwan banned toddlers under the age of two from using mobile phones or any similar electronic devices, and France banned WiFi from toddlers' nurseries.

As the market increases to grow, more light is being shed upon the accompanying behavioural health issues and how mobile phones can be problematic. Mobile phones continue to become increasingly multifunctional and sophisticated, which this in turn worsens the problem.

Prevalence of mobile phone overuse depends largely on definition and thus the scales used to quantify a subject's behaviors. Two scales are in use, the 20-item self-reported Problematic Use of Mobile Phones (PUMP) scale, and the Mobile Phone Problem Use Scale (MPPUS), which have been used both with adult and adolescent populations. There are variations in the age, gender and percentage of the population affected problematically according to the scales and definitions used. The prevalence among British adolescents aged 11–14 was 10%. In India, addiction is stated at 39-44% for this age group. Under different diagnostic criteria, the estimated prevalence ranges from 0 to 38%, with self-attribution of mobile phone addiction exceeding the prevalence estimated in the studies themselves. The prevalence of the related problem of Internet addiction was 4.9-10.7% in Korea, and is now regarded as a serious public health issue.

Behaviors associated with mobile-phone addiction differ between genders. Women are more likely to develop addictive mobile phone behavior than men. Men experience less social stress than women and use their mobile phones less for social purposes. Older people are less likely to develop addictive mobile phone behavior because of different social usage, stress and greater self-regulation.

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.

The rate of people who have problems of shopping addiction is a very controversial matter, because the dividing line between pathological behaviours and those behaviours which, even if excessive, are socially accepted, is very difficult to determine. However, shopping addiction and other manifestations of the lack of self-control on spending are widespread problems which are constantly expanding. Studies using samples of the general population show that between 8% and 16% of the people have problems with excessive or uncontrolled purchases. Clinical studies give much lower figures, however, between 2% and 5%. According to the European Report on the programme for the prevention and treatment of personal problems related to consumer addiction, personal purchasing habits and over-indebtedness, 3% of European adults and 8% of European young people have a level of shopping addiction which could be considered as pathologic, that is, which seriously affects the life of the people who suffer from this. Other estimates for the prevalence of compulsive buying range from a low of 2 percent to 12 percent or more (in the U.S. population.

Most of people who have these problems neither receive nor ask for treatment. Those that ask for help only do it after years of suffering, when the addiction has caused very serious economic repercussion and has harmed the relationship with their family and social environment. For this reason and due to the lack of social consciousness about this problem, the unrecorded figure of people who suffer from these problems is very high. In addition to the severe cases of shopping addiction, an important part of consumers (between 30% and 50% of the population) have deficiencies with spending self-control or excessive purchases. According to the European Report, 33% of European adults and 46% of the European young people have minor or moderate problems with shopping addiction or lack of economic self-control.

Computer addiction can be described as the excessive or compulsive use of the computer which persists despite serious negative consequences for personal, social, or occupational function. Another clear conceptualization is made by Block, who stated that "Conceptually, the diagnosis is a compulsive-impulsive spectrum disorder that involves online and/or offline computer usage and consists of at least three subtypes: excessive gaming, sexual preoccupations, and e-mail/text messaging". While it was expected that this new type of addiction would find a place under the compulsive disorders in the DSM-5, the current edition of the "Diagnostic and Statistical Manual of Mental Disorders", it is still counted as an unofficial disorder. The concept of computer addiction is broadly divided into two types, namely offline computer addiction and online computer addiction. The term offline computer addiction is normally used when speaking about excessive gaming behavior, which can be practiced both offline and online. Online computer addiction, also known as Internet addiction, gets more attention in general from scientific research than offline computer addiction, mainly because most cases of computer addiction are related to the excessive use of the Internet.

Although addiction is usually used to describe dependence on substances, addiction can also be used to describe pathological Internet use. Experts on Internet addiction have described this syndrome as an individual being intensely working on the Internet, prolonged use of the Internet, uncontrollable use of the Internet, unable to use the Internet with efficient time, not being interested in the outside world, not spending time with people from the outside world, and an increase in their loneliness and dejection. However, simply working long hours on the computer does not necessarily mean someone is addicted.

Video game addiction (VGA) is a hypothetical behavioral addiction characterized by excessive or compulsive use of computer games or video games, which interferes with a person's everyday life. Video game addiction may present itself as compulsive gaming, social isolation, mood swings, diminished imagination, and hyper-focus on in-game achievements, to the exclusion of other events in life.

In May 2013, the American Psychiatric Association (APA) proposed criteria for video game addiction in the 5th edition of the "Diagnostic and Statistical Manual of Mental Disorders", concluding that there was insufficient evidence to include it as an official mental disorder. However, proposed criteria for "Internet Gaming Disorder" were included in a section called "Conditions for Further Study".

While Internet gaming disorder is proposed as a disorder, it is still discussed how much this disorder is caused by the gaming activity itself, or whether it is to some extent an effect of other disorders. Contradictions in research examining video game addictiveness may reflect more general inconsistencies in video game research. For example, while some research has linked violent video games with increased aggressive behavior other research has failed to find evidence for such links.

Some scholars believe that codependency is not a negative trait, and does not need to be treated, as it is more likely a healthy personality trait taken to excess. Codependency in nonclinical populations has some links with favourable characteristics of family functioning.

Stan Katz states that codependence is over-diagnosed, and that many people who could be helped with shorter-term treatments instead become dependent on long-term self-help programs. The language of, symptoms of, and treatment for codependence derive from the medical model suggesting a disease process underlies the behavior. However, there is no evidence that codependence is caused by a disease process.

In their book, “Attached.”, Dr. Amir Levine and Rachel S. F. Heller, address what they call the “codependency myth” by asserting that attachment theory is a more scientific and helpful model for understanding and dealing with attachment in adults.

Some theorists focus on presumed built-in reward systems of the games to explain their potentially addictive nature. Many video games, particularly massively multiplayer online role-playing games and social network and mobile games, rely on a "compulsion loop" or "core loop", a cycle of activities that involve rewarding the player and driving them to continue through another cycle, retaining them in the game. The anticipation of such rewards can create a neurological reaction that releases dopamine into the body, so that once the reward is obtained, the person will remember it as a pleasurable feeling. This has been found similar to the same neurological reaction believed to be associated with gambling addiction. In reference to gamers such as one suicide in China, the head of one software association was quoted, "In the hypothetical world created by such games, they become confident and gain satisfaction, which they cannot get in the real world."

Griffiths has also proposed that another reason why online video games are potentially addictive is because they "can be played all day every day". The fact that there is no end to the game can feel rewarding for some, and hence players are further engaged in the game.

A high prenatal testosterone load may be a risk factor for the development of video game addiction in adulthood.

Ferguson, Coulson and Barnett in a meta-analytic review of the research, concluded that the evidence suggests that video game addiction arises out of other mental health problems, rather than causing them. Thus it is unclear whether video game addiction should be considered a unique diagnosis.

Researchers at the University of Rochester and Immersyve, Inc. (a Celebration, Florida, computer gaming think-tank) investigated what motivates gamers to continue playing video games.

According to lead investigator Richard Ryan, they believe that players play for more reasons than fun alone.

Ryan, a motivational psychologist at Rochester, says that many video games satisfy basic psychological needs, and players often continue to play because of rewards, freedom, and a connection to other players.

Michael Brody, M.D., head of the TV and Media Committee of the American Academy of Child and Adolescent Psychiatry, stated in a 2007 press release that "... there is not enough research on whether or not video games are addictive". However, Brody also cautioned that for some children and adolescents, "... it displaces physical activity and time spent on studies, with friends, and even with family".

Karen Pierce, a psychiatrist at Chicago's Children's Memorial Hospital, sees no need for a specific gaming addiction diagnosis. Two or more children see her each week because of excessive computer and video game play, and she treats their problems as she would any addiction. She said one of her excessive-gaming patients "...hasn't been to bed, hasn't showered...He is really a mess".

Research carried out on people undergoing treatment, as well as on the general population has revealed a negative correlation between age and addiction. As the age of people increases there is a lower number of shopping addicts. This data was confirmed by the 1999 European Report.

It must be noted that the age of diagnosis is much later than the age when the problems of addiction begin. Most addicts have the first symptoms of addiction in their twenties, but do not ask for help nor accept treatment until more than ten years afterwards. To explain the higher incidence of shopping addiction in young people, it has been shown that younger people have been born, and have grown up, in an increasingly consumerist society and they have endured the impact of publicity and marketing from birth. On the contrary, it is very unusual to find shopping addiction problems in people older than 65 years.

Codependency can occur in any type of relationship, including family, work, friendship, and also romantic, peer or community relationships.

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.

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.

Both casinos and poker machines in pubs and clubs facilitate problem gambling in Australia. The building of new hotels and casinos has been described as "one of the most active construction markets in Australia"; for example, AUD$860 million was allocated to rebuild and expand the Star Complex in Sydney.

A 2010 study, conducted in the Northern Territory by researchers from the Australian National University (ANU) and Southern Cross University (SCU), found that the proximity of a person's residence to a gambling venue is significant in terms of prevalence. Harmful gambling in the study was prevalent among those living within 100 metres of any gambling venue, and was over 50% higher than among those living ten kilometres from a venue. The study's data stated:

"Specifically, people who lived 100 metres from their favourite venue visited an estimated average of 3.4 times per month. This compared to an average of 2.8 times per month for people living one kilometre away, and 2.2 times per month for people living ten kilometres away".

According to the Productivity Commission's 2016 report into gambling, 0.5% to 1% (80,000 to 160,000) of the Australian adult population suffered with significant problems resulting from gambling. A further 1.4% to 2.1% (230 000 to 350 000) of the Australian adult population experienced moderate risks making them likely to be vulnerable to problem gambling. Estimates show that problem gamblers account for an average of 41% of the total gaming machine spending.

Over the past decade, the concept of Internet addiction has grown in terms of acceptance as a legitimate clinical disorder often requiring treatment. Researchers are divided over whether Internet addiction is a disorder on its own or a symptom of another underlying disorder. There is also debate over whether it should be classified as an impulse-control disorder or an obsessive-compulsive disorder rather than an addiction.

While the existence of Internet addiction is debated, self-proclaimed sufferers are resorting to the courts for redress. In one American case ("Pacenza v. IBM Corp."), the plaintiff argued he was illegally dismissed from his employment in violation of the Americans with Disabilities Act because of Internet addiction triggered by Vietnam War-related post-traumatic stress disorder (PTSD). The case was dismissed by the United States District Court for the Southern District of New York and affirmed on appeal to the United States Court of Appeals, Second Circuit in 2010 (case summarized in Glaser & Carroll, 2007).

About 25% of users fulfill Internet addiction criteria within the first six months of using the Internet. Many individuals initially report feeling intimidated by the computer but gradually feel a sense of "competency and exhilaration from mastering the technology and learning to navigate the applications quickly by visual stimulation" (Beard 374). The feeling of exhilaration can be explained by the way IAD sufferers often describe themselves as: bold, outgoing, open-minded, intellectually prideful, and assertive.

According to a study by Kathy Scherer, a psychologist from the University of Texas at Austin, "13% of college internet users fit the criteria for Internet addicts" (Scherer 1997). In her study, Scherer enlisted the help of 531 college students. She discovered that "72% of the Internet addicted students were men" (Scherer 1997).

The China Communist Youth League claimed in 2007 that over 17% of Chinese citizens between 13 and 17 were addicted to the Internet.

Public concern, interest in, and the study of, Internet over use can be attributed to the fact that it has become increasingly difficult to distinguish between the online and offline worlds. The Internet has tremendous potential to affect the emotions of humans and in turn, alter our self-perception and anxiety levels.

According to Maressa Orzack, director of the Computer Addiction Study at Harvard University's McLean Hospital, between 5% and 10% of Web surfers suffer some form of Web dependency.

According to the Center for Internet Addiction Recovery (whose director is Kimberly S. Young, a researcher who has lobbied for the recognition of net abuse as a distinct clinical disorder), "Internet addicts suffer from emotional problems such as depression and anxiety-related disorders and often use the fantasy world of the Internet to psychologically escape unpleasant feelings or stressful situations." More than half are also addicted to alcohol, drugs, tobacco, or sex.

Mark Griffiths states that "[t]he way of determining whether nonchemical (i.e., behavioral) addictions are addictive in a nonmetaphorical sense is to compare them against clinical criteria for other established drug-ingested addictions", and although his data is dated, and may no longer represent average Internet use accurately, Griffiths comes to the conclusion that the Internet does meet that criteria for addiction in a small number of users.

Scientists have found that compulsive Internet use can produce morphological changes in the structure of the brain. A study which analyzed Chinese college students who had been classified as computer addicts by the study designers and who used a computer around 10 hours a day, 6 days a week, found reductions in the sizes of the dorsolateral prefrontal cortex, rostral anterior cingulate cortex, supplementary motor area and parts of the cerebellum compared to students deemed "not addicted" by the designers. It has been theorized that these changes reflect learning-type cognitive optimizations for using computers more efficiently, but also impaired short-term memory and decision-making abilities—including ones in which may contribute to the desire to stay online instead of be in the real world.

Patricia Wallace PhD, Senior Director, Information Technology and CTY Online, at the Johns Hopkins University Center for Talented Youth argues that based on the case histories that have surfaced, no one denies that excessive involvement with certain psychological spaces on the net can have serious effects on a person's life. She explains that, at a large university in New York, the dropout rate among freshmen newcomers rose dramatically as their investment in computers and Internet access increased, and the administrators learned that 43% of the dropouts were staying up all night on the Internet.

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.

25% of male weightlifters reported memories of childhood physical or sexual abuse in an interview. Anabolic steroids are sometimes used by people with muscle dysmorphia (a very specific type of body dysmorphic disorder (BDD)) as a defense mechanism. Interestingly, yohimbine, while considered something of a flop as a supplement for failing to increase testosterone levels as had at first been suspected, has at higher doses been discovered to be useful in facilitating recall of traumatic memories during post traumatic stress disorder (PTSD) treatment.

Male anabolic-androgenic steroid abusers often have a troubled social background.

Digital hoarding (also known as e-hoarding) is excessive acquisition and reluctance to delete electronic material no longer valuable to the user. The behavior includes the mass storage of digital artifacts and the retainment of unnecessary or irrelevant electronic data. The term is increasingly common in pop culture, used to describe the habitual characteristics of compulsive hoarding, but in cyberspace. As with physical space in which excess items are described as "clutter" or "junk," excess digital media is often referred to as "digital clutter."

Cash, Rae and Winkler, in a paper titled "Internet Addiction: A brief summary of research and practice", describe early interventions used in the treatment of Internet addiction (IAD), and Internet Gaming Disorder (IGD).

Cognitive Behavior Therapy is designed to help individuals learn how to control their thoughts and feelings. This control is to prevent harmful functions that may trigger impulses to escape into the virtual world. The therapy is setup for three stages. The first stage is to instruct the patient to identify there is a problem and how much a problem computers are creating. Identification is done by using a log to document duration, events, day, of online activity. This can be used to show in black and white how much time is spent online and to help create a realistic goal for patients to strive for. Using this log the patients interact with a therapist to make a schedule for online activity to promote new healthier habits. The second aspect of the treatment program is more for the cognitive aspect, as in, digging into what triggers the excessive online activity. The third phase is to confront or resolve the issues in the patient's life that lead to them seeking escape things via the Internet.

One source states that a major reason the Internet is so appealing is the lack of limits and the absence of accountability.

Professionals generally agree that, for Internet overuse, controlled use is a more practical goal than total abstinence.

Families in the People's Republic of China have turned to unlicensed training camps that offer to "wean" their children, often in their teens, from overuse of the Internet. The training camps have been associated with the death of at least one youth. In November 2009, the government of the People's Republic of China banned physical punishment to "wean" teens from the Internet. Electro-shock therapy had already been banned.

In August 2013, researchers at the MIT Media Lab developed a USB-connected keyboard accessory that would "punish" users – with a small electric jolt – who spent too much time on a particular website.

In July 2014, an internet de-addiction center was started in Delhi, the capital city of India by a non profit organization, Uday Foundation. The Foundation provides counseling to the children and teens with internet addiction disorder.

In August 2009, "ReSTART", a United States-based residential treatment center for "problematic digital media use, internet addiction, and video game addiction", opened near Seattle, Washington, United States. It offers a 7- to 12-week intensive program for adolescents and adults intended to help people set device limits, and address digital distractions.

In 2005, Professor Kiesler called Internet addiction a fad illness. In her view, she said, television addiction is worse. She added that she was completing a study of heavy Internet users, which showed the majority had sharply reduced their time on the computer over the course of a year, indicating that even problematic use was self-corrective.

There are approximately 976 million smokers in the world. Estimates are that half of smokers (and one-third of former smokers) are dependent based on DSM criteria, regardless of age, gender or country of origin, but this could be higher if different definitions of dependence were used. Recent data suggest that, in the United States, the rates of daily smoking and the number of cigarettes smoked per day are declining, suggesting a reduction in population-wide dependence among current smokers. However, there are different groups of people who are more likely to smoke than the average population, such as those with low education or low socio-economic status and those with mental illness. There is also evidence that among smokers, some subgroups may be more dependent than other groups. Men smoke at higher rates than do women and score higher on dependence indices; however, women may be less likely to be successful in quitting, suggesting that women may be more dependent by that criterion. Higher nicotine dependence has also been linked with mental illness, including anxiety and depression.

The consequences of oniomania, which may persist long after a spree, can be devastating, with marriages, long-term relationships, and jobs all feeling the strain. Further problems can include ruined credit history, theft or defalcation of money, defaulted loans, general financial trouble and in some cases bankruptcy or extreme debt, as well as anxiety and a sense of life spiraling out of control. The resulting stress can lead to physical health problems and ruined relationships, or even suicide.

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 form of behavior that is still being investigated is obsessive sun tanning as a behavioral addiction. In a recent study, researchers have proved that many frequent tanners demonstrate signs and symptoms adapted from substance abuse or dependence criteria. Many people who admit to being frequent tanners say they tan to look good, feel good, and to relax. People who partake in excessive tanning are usually completely aware of the health risks associated with it, just like addicted smokers are completely aware of the health risks of smoking. The health hazards are even more severe for high-risk age groups such as teenagers and young adults. Due to the fact that the health risks do not deter tanners from their habit, they are exhibiting self-destructive behavior that resembles the characteristics of those who suffer from substance abuse.

Frequent tanners have said a primary reason why they participate in artificial tanning is to experience the "feel good" feeling tanning salons have to offer. Researchers have found that ultraviolet (UV) radiation from tanning beds offers mood-enhancing effects that act as a treatment for seasonal affective disorder (SAD). SAD is when a person exhibits minor depression during seasonal changes, such as during the winter months. Ultraviolet radiation has been proven to increase the level of melatonin in the body. Melatonin plays a key role in sleep patterns and is suggested to reduce anxiety levels. Thus, those who go tanning experience a sense of relaxation afterwards. This sensation is what possibly drives tanners to continue tanning regardless of the health risks. More research needs to be done, but many researchers are beginning to add tanning to the list of addictive processes.

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.

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.