• Authors
  • Department of Applied Social Sciences, The Hong Kong Polytechnic University, Hong Kong, P. R. China
  • Division of Learning, Development and Diversity, Department of Education, Faculty of Education, The University of Hong Kong, Hong Kong, P. R. China
  • Department of Applied Social Sciences, The Hong Kong Polytechnic University, Hong Kong, P. R. China
FREE ARTICLE

Internet Addiction

Abstract

The Internet has become a basic tool for trading, entertainment, communication, as well as education in the contemporary world. Nevertheless, despite the high speed of information flow and potential educational value of the Internet, there are several attributes of the Internet which may foster addictive behavior. These attributes include easy and flexible access 24 hours a day; anonymity; provision of free, diversified, and unlimited number of social networks without geographical boundaries; greater control over one's self-presentation; and provision of numerous opportunities to fulfill the need for belongingness as well as to escape from emotional difficulties, problematic situations, and personal hardships.

Internet addiction commonly refers to an individual's inability to control his or her use of the Internet (including any online-related, compulsive behavior) which eventually causes one's marked distress and functional impairment in daily life. Research findings have shown that excessive use of Internet or Internet addiction adversely affects one's physical health, family life, and academic performance. Concerning the negative consequences of Internet addiction on one's physical health, persistence of sleep deprivation may harm one's immune system, thus increasing one's vulnerability to assorted diseases. The lack of exercise due to excessive use of computer by maintaining a sitting posture may also risk suffering from carpal tunnel syndrome, back pain, and eyestrain. Concerning family problems caused by Internet addiction, family relationships are seriously disrupted by Internet addicts due to the decrease in time spending with family, reluctance of performing family duties such as doing household chores, and increase of conflicts with family in the negotiation for time spent on the Internet. Academic problems caused by Internet addiction include decline in study habits, significant drop in grades, missing classes, increased risk of being placed on academic probation, and poor integration in extracurricular activities. Besides, adolescent Internet addicts often suffer from severe psychological distress, such as depression; anxiety; compulsivity; feeling of self-effacement; fear that life without Internet would be boring, empty, and joyless; as well as feeling of loneliness and social isolation. In addition, people addicted to the Internet games may excessively imitate the behaviors and values of the characters in online games.
In view of the possible negative influence of Internet addiction on human development, there is a need to have a thorough understanding of the nature of Internet addiction. There are several sections in this chapter. First, a historical review of Internet addiction is presented. Second, the conceptualization and assessment of Internet addiction are discussed. Third, prevalence data of Internet addiction are described. Fourth, major theoretical accounts of Internet addiction are presented. Fifth, risk factors and protective factors related to Internet addiction are discussed. Sixth, intervention models of Internet addiction are outlined. Finally, the future research directions are examined.
Abbreviations
ADHD Attention deficit hyperactivity disorder - APA American psychological association - CBT Cognitive-behavioral therapy - DSM-IV Diagnostic and statistical manual (4th edition) of the American Psychiatric Association - DSM-V Diagnostic and statistical manual (5th edition) of the American Psychiatric Association - IA Internet addiction - IAD Internet addiction disorder - IAT Internet addiction test - ICD Impulse control disorder - IRABI Internet-related addictive behavior inventory - ITAA Internet and technology addiction anonymous - MI Motivational interviewing - OARS Open-ended questions affirmations, reflective listening, and summarization - OCD Obsessive-compulsive disorder - PCU Pathological computer use - PIU Problematic Internet use - PIUQ Problematic Internet Use Questionnaire - RtC Group therapy treatment with a combination of readiness to change - SSRI Selective serotonin reuptake inhibitor

Brief History

Historical Development

The initial idea of Internet as a way of "data communication" was first proposed in the early 1960s by a group of American computer scientists who saw great potential value in allowing scientists to share information on research and development in scientific fields via computers. During the 1980s, the use of Internet developed quickly, and by 1995 the Internet had become a mainstream communication vehicle (Shaffer et al. 2000). From then on, as with the functionality of Internet, the number of Internet users has expanded dramatically across the world. Today, as a collection of various services and resources, the Internet has become the most ever powerful tool for human being. Just as a popular saying goes, "Internet has brought a globe in a single room, and even the palm of one's hand."

While it is evident that the Internet has greatly altered modern lives by its accessibility and convenience, possible misuses and destructive effects of the Internet have not gone unnoticed. The presence of addictive behaviors among some Internet users has drawn the attention of the public and helping professionals since the early 1990s. Research into the potential problems of excessive Internet use has increased substantially over the past two decades.

In 1995, an article entitled "The Lure and Addiction of Life On Line," published in the New York Times, first raised the concerns of a wider public about the potential harms of uncontrollable Internet use. By quoting addiction experts and computer industry professionals, the author linked excessive Internet use with other behavioral addiction such as compulsive gambling, shopping, and substance abuse. In the same year, Ivan Goldberg borrowed criteria for defining psychoactive substance dependence in the DSM-IV and first coined the term "Internet addiction disorder" to represent those having problematic Internet use behavior. In June 1996, an article first appeared in the American Psychological Association's trade newspaper, the APA Monitor, described cases of college students who suffered from academic failure and poor social relationships due to Internet misuse. In this article, Bridget Murray cautioned that the Internet might potentially lead to addictive behaviors among users and suggested the psychology community to develop guidelines for treating people who may be addicted to the Internet (Murray, 1996).

Similarly, as a leading expert in the field of problematic Internet use behavior, Kimberly Young presented the first empirical research on Internet addiction in 1996 at the American Psychological Association's annual conference in her paper entitled "Internet Addiction: The Emergence of a New Disorder." In this paper, Young adapted the criteria for pathological gambling defined by the DSM-IV (American Psychiatric Association, 1994) to diagnose the Internet addiction as a compulsive disorder. Young also developed the 7-item, 8-item, 10-item, and 20-item scales, namely, the Internet Addiction Test, for assessing "Internet dependent" or "Internet addicted" behavior. In one of her early studies with a sample of 596 self-selected Internet users, Young found that 66% of the respondents could be classified as "Internet dependent," who displayed an array of addictive behaviors including tolerance, loss of control, withdrawal, and impairment of functioning. Among these identified individuals, negative academic, social, financial, and occupational consequences caused by Internet addiction were also observed. Based on these findings, Young pointed out that Internet addiction adversely affected one's physical health, family life, and academic performance and ought to be designated as a mental disorder. Since then, a lot of research and debates about Internet addiction have been generated.

Griffiths regarded Internet addiction as a form of technological addiction under the category of behavioral addiction. He proposed six core components of Internet addiction, including salience (Internet dominates one's life), mood modification (Internet changes the mood of the user), tolerance (increasing time spent to obtain the desired effect), withdrawal symptoms (unpleasant physical and psychological reactions when Internet activity is reduced or curtailed), conflicts (intraindividual and interindividual conflicts because of Internet behavior), and relapse (tendency to revert to earlier pattern of addictive behavior). Young described how Internet addiction is akin to substance addiction through providing a self-medicating effect, allowing for avoidant behaviors and brief emotional relief. She also proposed four types of triggers that serve as the initiation of excessive Internet use: (1) applications: a specific function of Internet that is particularly problematic for the user; (2) emotions: being online is gratifying and calming while blocking pain, uncertainty, or discomfort; (3) cognition: being online is a relief from maladaptive thoughts and catastrophic thinking; and (4) life events: dissatisfaction with one or multiple areas of life. Singularly or in combination, these conditions could lead a person to be more prone to Internet addiction.

In addition to Young's Internet Addiction Test, there are other attempts to construct Internet addiction measurements. For example, Brenner developed a 32-item questionnaire entitled "Internet-Related Addictive Behavior Inventory" (IRABI) to assess Internet addiction and found that most of the respondents experienced at least one of the Internet addiction symptoms, including tolerance, craving, and withdrawal. Egger and Rauterberg also designed a self-reported questionnaire to examine Internet behaviors and addiction tendency of 454 Internet users in Switzerland and other European countries, and reported that 10.6% of the respondents were addicted to or dependent on the Internet.

Different terms have been used to describe Internet addiction problems, such as problematic Internet use (PIU), pathological computer use (PCU), and Internet addiction disorder (IAD). The Centre for On-Line Addiction (1998) identified five specific types of Internet addiction:
  1. Cybersexual addiction - Addiction to cyber-pornographic materials and interaction (such as adult chat rooms)
  2. Cyber-relationship addiction - Addiction to online friendship which replaces one's relationships with friends and family in real life
  3. Net compulsion - Obsessive online activities including online gambling, online auction, and online trading
  4. Information overload - Obsessive web surfing or searches of databases
  5. Computer addiction - Excessive computer game playing or efforts paid to computer programming

Intervention for Internet Addiction

Research studies in the Western and Asian contexts have also suggested that the risk of Internet addiction is rising especially among young people. In response to the negative consequences and the increasing risk of Internet addiction, there is a need to explore intervention models to help Internet addicts. Over the years, an array of therapeutic strategies has been developed to treat Internet addiction based on different theoretical foundations. The first treatment facility designed to specifically deal with Internet addiction is Kimberly Young's Center for Internet Addiction Recovery, founded in 1995. The center offers visitors educational resources on Internet addiction; a set of online self-assessment tools to determine whether one has Internet addiction; and different forms of counseling services for self-identified Internet addicts, including both face-to-face counseling for individuals, couples, and families and e-counseling through telephone and online communication. The major treatment strategy adopted in the center is the cognitive-behavioral therapy plus psycho-education. In addition, seminars and workshops are provided in the center to train mental health practitioners in diagnosis, clinical assessment, and treatment of Internet addiction.

Some important research and treatment work has been conducted in South Korea, China, and other Asian areas. After a series of 10 cardiopulmonary-related deaths induced by compulsive Internet use in Internet bars and a game-related murder, South Korean government views Internet addiction as one of its most serious public health issues and starts to carry out substantial research on Internet addiction. China has also shown great concerns about the disorder because of the dramatic increase of Internet use among Chinese adolescents in the last decade. According to a national report in 2007, there are around 10 million Chinese teenagers who meet Internet addiction diagnostic criteria. As a result of the considerable attentions given to this problem, South Korea and China have officially recognized and treated Internet addiction as a psychiatric disorder. In South Korea, the government has trained 1,000 counselors to specifically help the 200,000 children believed to be addicted to the Internet. Similarly, Chinese government has officially designated hospital psychiatric units and Internet addiction recovery centers to treat cases of Internet addiction since 2008.

Contrasting with the active efforts to address the problems related to Internet addiction in Asian countries, Internet addiction has not been recognized as a separate disorder by the American Psychiatric Association and the treatment is generally not covered by medical insurance. Although research shows that Internet addiction is a concerning psychological impairment, with regard to whether Internet addiction should be diagnosed as a mental disorder, there have been considerable debates among Western researchers. Some experts insisted that excessive use of Internet is a secondary manifestation of other mental disorders to counteract other psychological deficiencies or to fulfill other psychological needs associated with underlying disorders. Consequently, Internet addiction is symptomatic in nature, which should not be considered as a true addiction or a specific disorder. On the other hand, an increasing number of clinicians and psychologists support for the inclusion of Internet addiction as a real disorder in DSM-V. They pointed out that symptoms of Internet addiction mirror other compulsive/impulsive disorders, including excessive use, withdrawal, tolerance, and negative repercussions, akin to other addictive disorders in that some Internet services (like online shopping, gambling, and sex) have unique psychological properties which induce dissociation, time distortion, and instant gratification that can produce a mood-altering effect, and more importantly, excessive Internet use has directly caused severe functional impairments in different aspects of the users' lives. Therefore, Internet addiction is worthy of a standardized definition and of diagnostic criteria.

Now, the American Psychiatrist Association is considering the inclusion of Internet addiction in the new revision of the DSM-V, and there has been a general recognition among clinical practitioners that patients having difficulties in controlling their impulses to use the Internet need to be treated no matter how this behavior is classified. Despite of this, the continuous controversy has inevitably hindered the development of effective treatment protocols specifically designed for Internet addictive patients. For example, patients may not be able to receive a systematic treatment program because they cannot afford the therapeutic fee which is not covered by their medical insurance.

Over the years, hospitals and clinics have emerged with outpatient treatment services for Internet addiction recovery, and in some cases addiction rehabilitation centers have admitted people with Internet addiction into inpatient care. Social service organizations and college campuses have also started intervention programs and support groups to help youth and students who are addicted to the Internet. In 2009, the first residential treatment center for Internet addiction in the United States, called reSTART, was opened in the suburb of Seattle. The reSTART offers a 45-day abstinence-based recovery program for people with pathological computer use. Sessions of the program range from individual and group counseling and psychotherapy to life skills and vocational coaching, physical education, and a variety of recreational activities. A few treatment procedures have been developed to help people with Internet addiction, including group therapy treatment with a combination of readiness to change (RtC), cognitive-behavioral therapy (CBT), motivational interviewing (MI) interventions, as well as reality therapy group counseling program. Some of the programs were developed to help clients with specific Internet addiction, such as Internet-addicted sexual behavior, and the protocols of those programs were not presented in details. Young reported that cognitive-behavioral therapy techniques were effective in decreasing the addictive thoughts and behaviors related to Internet both in the short-term assessment and 6-month follow-up. Clearly, more experimentally designed evaluative studies that employ randomized control groups are needed to demonstrate the effectiveness of different intervention programs.

Relevant Journals and Websites

Since the inception of the term, Internet addiction has been a hot topic not only in the mass media but also in the scientific community. Research findings on Internet addiction are widely reported in a variety of academic publications across multiple disciplines ranging from psychiatry, psychology, social work, education, to laws, economics, and even computer sciences. In the field of psychiatry, several highly prestigious journals, such as "The American Journal of Psychiatry," "Psychiatrist," and "Advances in Psychiatric Treatment," publish Internet addiction studies, reviews, and editorials. In the broad area of social sciences, such findings frequently appear in "CyberPsychology & Behavior" (now the "CyberPsychology, Behavior, and Social Networking"), "American Psychologist," "Addictive Behaviors," "Journal of School Health," "Psychiatry, Psychology, and Law," "Educational Psychological Review," and others. Another information dissemination outlet of Internet addiction research consists of computing journals such as "Computers & Education," "Computer in Human Behavior," and "Journal of Human Computer Studies." Among all these journals, "CyberPsychology & Behavior" is now the leading publication for Internet addiction research, aiming at exploring the impact of the Internet, multimedia, and virtual reality on behavior and society. There are also a few websites providing useful information, resources, therapeutic services, or referral sites for people who might be addicted to Internet, their friends and family, and practitioners who work on Internet addiction, such as the following:
  1. The Centre for Internet Addiction Recovery (http://www.netaddiction.com)
  2. Virtual-Addiction (http://www.virtual-addiction.com/)
  3. The reSTART Internet addiction recovery Program (http://www.netaddictionrecovery.com/)
  4. Illinois Institute for Addiction Recovery (http://www.addictionrecov.org)
  5. Daily Strength (http://www.dailystrength.org/c/Internet-Addiction/support-group)
  6. Computer Addiction Services (http://www.computeraddiction.com)
  7. Psych Central (http://psychcentral.com/netaddiction/)

Conceptualization of Internet Addiction

Since Ivan Goldberg borrowed the criteria of substance abuse in DSM-IV to define the "Internet addiction disorder" in 1995, there have been many debates on whether Internet addiction should be regarded as a psychiatric disorder and how it should be assessed. While some researchers link Internet addiction to obsessive-compulsive disorder (OCD) and impulse control disorder (ICD), there are views arguing that IA does not deserve its own diagnostic criteria due to the difficulty on determining whether IA develops on its own or not. Besides, while some researchers suggest that there are similarities between Internet compulsion and compulsive gambling, some argue that it might be more appropriate to use the term "problematic" or "maladaptive" to describe Internet overuse. Some even argue that people would go from overuse to "normal" use eventually, while the overuse is only a transition phase. Other views suggest that one must be very careful to draw a line between "normal overenthusiasm" in using the Internet and "abnormal preoccupation" with Internet use.

There are several issues intrinsic to the conceptualization of Internet addiction as a form of mental problem. First, in terms of diagnostic criteria, it is important to ask whether there is a consistent set of symptoms and syndromes that are observed and diagnosed. Second, the question of whether the diagnostic criteria demonstrate validity should be asked. Third, it is important to ask whether Internet addictive behavior should be seen as a separate mental disorder or part of a specific form of mental disorder. There are research findings showing that problematic Internet use is associated with other forms of mental disorders such as obsessive-compulsive disorder and depression. Regarding such observed relationships, there are several possibilities. First, psychiatric symptoms may lead to the occurrence of problematic Internet use. Second, Internet addiction may lead to the onset of psychiatric symptoms. Third, psychiatric symptoms and problematic Internet use may influence each other. Finally, the relationship between the two domains may be due to shared genetic or environmental factors.

Generally speaking, concepts such as compulsive use, tolerance, withdrawal, and impairment of psychosocial functioning, particularly those related to substance abuse and impulse control disorders, are used to define Internet addictive behavior. Internet addiction has been understood in terms of drug addiction and pathological gambling in the Diagnostic and Statistical Manual (4th edition) of the American Psychiatric Association. In the DSM-IV, substance abuse is defined as a maladaptive pattern of substance use which leads to significant impairment or distress, as shown by one or more of the following behaviors occurring within a 12-month period: (1) failure to fulfill major role obligations at work, school, or home due to recurrent substance use (e.g., impaired work performance or absences because of substance use, impaired school performance or absences related to substance use, home management problems as a result of drug use); (2) using substance in situations in which it is physically dangerous (e.g., driving an automobile under the influence of drugs); (3) recurrent legal problems because of taking drugs; or (4) although substance abuse has caused persistent or recurrent social or interpersonal problems, the person still uses drugs.

Translating the above criteria to Internet abuse, Internet abuse can be understood as a maladaptive pattern of Internet use which leads to significant impairment or distress, as shown by one or more of the following behaviors occurring within a 12-month period: (1) failure to fulfill major role obligations at work, school, or home (e.g., impaired work performance or absences because of Internet use, impaired school performance or absences because of Internet use, home management problems as a result of Internet use); (2) using Internet in situations in which it is physically dangerous (e.g., continuous and prolonged use of Internet without rest, long duration of stay in Internet bars); (3) recurrent legal problems because of using Internet (e.g., illegal downloading and Internet stealing); or (4) continuous use of Internet despite the persistent or recurrent social or interpersonal problems caused by Internet abuse.

Substance dependence is a more serious problem compared to substance abuse, which is accompanied by certain changes in the way the person uses substance. According to DSM-IV, substance dependence (or addiction) refers to a maladaptive pattern of substance use which leads to clinically significant impairment or distress, with the person displaying three or more of the characteristics in the same 12-month period. The characteristics include (1) tolerance as shown by either a need to increase the amount of the substance to achieve the desired effect or experiencing diminished effect with continued use of the same amount of the substance; (2) withdrawal symptoms, as manifested by either the characteristic withdrawal syndrome for the substance or taking the same (or closely related) substance to relieve or avoid withdrawal symptoms; (3) amount of drug taken or period of taking is greater than what is intended; (4) the person has a persistent desire or unsuccessful effort to cut down or control substance use; (5) much time is spent to obtain or use the substance or to recover from its effect; (6) substance abuse has led to the giving up or reduction of important social, occupational, or recreational activities; and (7) continued drug use despite knowing that drug use has caused a persistent or recurrent physical or psychological problem.

Translating the above characteristics of substance dependence in DSM-IV to Internet addiction, Internet dependence can be defined as a maladaptive pattern of Internet use which leads to significant psychosocial impairment or distress, with the person displaying three or more of the characteristics in the same 12-month period. The characteristics include (1) tolerance as shown by either a need to increase the time spent on the Internet to achieve the desired effect or experiencing diminished effect with continued use of the same amount of Internet-related time and activities; (2) withdrawal symptoms; (3) amount of time and effort spent on the Internet is greater than what is intended; (4) the person has the desire to control Internet use or unsuccessful effort to cut down; (5) much time is spent to get access or use the Internet or to recover from its effect; (6) Internet use has led to the giving up or reduction of important social, occupational, or recreational activities; and (7) continued Internet use despite knowing that Internet use has caused a persistent or recurrent physical or psychological problem.

Besides drug addiction, pathological gambling has also been used by theorists to understand the nature of Internet addiction. In the DSM-IV, there are two diagnostic criteria for pathological gambling. First, it is characterized by persistent and recurrent maladaptive gambling behavior as indicated by five or more of the following signs: (1) preoccupation with gambling such as reliving past gambling experiences or thinking of ways to get money for gambling purpose; (2) need to gamble with more money in order to achieve the desired excitement; (3) experiencing repeated unsuccessful efforts to control, cut back, or stop gambling; (4) to cut down or stop gambling will lead to restlessness or irritability; (5) using gambling as a way of avoidance of problems or relief of dysphoric mood; (6) chasing after losing money; (7) lying to others to cover up the extent of involvement with gambling; (8) engaging in illegal activities to finance gambling; (9) adverse impact or loss of a significant relationship, job, or educational or career opportunity because of gambling; and (10) relying on others to provide money to cope with a desperate financial situation caused by gambling. The second criterion is that the gambling behavior is not better accounted for by a manic episode. These criteria were often employed/adapted by researchers in developing assessment tools and diagnostic criterion of Internet addiction.

Assessment of Internet Addiction

As far as assessment tools of Internet addiction are concerned, many instruments have been developed. Among the available measures, assessment tools developed by Ivan Goldberg and Kimberly Young are commonly used by researchers. According to these instruments, an individual is defined as Internet addict if he/she displays certain addictive behaviors in the past 12 months.

Young has developed several instruments assessing Internet addiction based on the concept of pathological gambling. The different versions are listed below.

Young's Brief 8-Item Questionnaire

According to Young, a person is considered "addicted" if he/she shows five or more of the following characteristics and when his/her behavior could not be better accounted for by a manic episode:
  1. Preoccupation with the Internet such as thinking about previous online activity or anticipating next online session
  2. Need to spend increasing amount of time online in order to achieve satisfaction
  3. Repeatedly unsuccessful efforts to control, cut back, or stop Internet use
  4. Suffering from withdrawal symptoms such as restlessness, moodiness, depression, or irritability when reducing Internet use
  5. Staying online longer than originally intended
  6. Internet use endangers or leads to the loss of significant relationship, job, or educational or career opportunity
  7. Telling lies to cover up problems created by Internet addiction
  8. Use of Internet to escape from problems or relieve from a dysphoric mood

Young's 10-Item Questionnaire

A person is defined as "Internet dependent" if he/she shows four or more of the following attributes:
  1. Feeling preoccupied with the Internet or online services and thinking about it while off-line
  2. Feeling a need to spend more and more time online to achieve satisfaction
  3. Being unable to control online use
  4. Feeling restless or irritable when attempting to cut down or stop online use
  5. Going online to escape from problems or relieve feelings such as helplessness, guilt, anxiety, or depression
  6. Lying to family members or friends to conceal excessive Internet use
  7. Risking the loss of a significant relationship, job, or educational or career opportunity because of online use
  8. Keeping on using the Internet even after spending too much money on online fees
  9. Showing withdrawal when off-line, such as increased depression, moodiness, or irritability
  10. Staying online longer than originally intended

Young's 7-Item Questionnaire

A person is defined as "Internet dependent" if he/she shows three or more of the following characteristics:
  1. Experiencing tolerance in that one needs for increased amounts of Internet use to achieve the desired effect or there is a diminished effect with continued use of the same time spent on the Internet
  2. Spending longer periods of time on the Internet than intended
  3. Spending a great deal of time in activities to stay online longer
  4. Giving up any social, occupational, or recreational activities because of the Internet
  5. Continuing to use the Internet despite knowledge of having a persistent or recurrent problem that is likely to have been caused or exacerbated by the Internet
  6. Having made unsuccessful attempts to cut down time spent online or lack of desire to cut down on the amount of time spent online
  7. Experiencing withdrawal symptoms (e.g., depression, irritability, moodiness, anxiety) when off-line
Besides Young, Goldberg also proposed seven criteria to assess Internet addiction by modifying the DSM-IV criteria for psychoactive substance dependence. A person is defined as having "Internet addiction disorder" if his/her Internet use behavior meets three or more of the following criteria:
  • Criteria I - Tolerance.
  • Criteria II - Withdrawal.
  • Criteria III - The Internet is accessed more often or for longer periods of time than was intended.
  • Criteria IV - There is a persistent desire or unsuccessful efforts to cut down or control Internet use.
  • Criteria V - A great deal of time is spent in activities related to Internet use.
  • Criteria VI - Important social, occupational, or recreational activities are given up or reduced because of Internet use.
  • Criteria VII - Internet use is continued despite knowledge of having a persistent or recurrent physical, social, occupational, or psychological problem.

There are other attempts to develop assessment tools of Internet addiction among researchers. Brenner designed a 32-item instrument, the Internet-Related Addictive Behavior Inventory (IRABI), for the measurement of Internet addiction. The items are devised to assess Internet use behaviors and experiences similar to those related to substance abuse defined in the DSM-IV. However, specific criteria to determine whether an individual is addicted to Internet were lacking in Brenner's study, and it is not clear whether items in the IRABI really capture behaviors that signify Internet addiction. In an online survey called the Virtual Addiction Survey, Greenfield (1999) used ten items adapted from DSM-IV criteria of pathological gambling to measure addicted Internet use patterns. Morahan-Martin and Schumacher (2000) developed a 13-item questionnaire to assess pathological Internet use in which those who answered "yes" to four or more of the 13 items were defined as pathological Internet users. Some of the items were akin to Brenner's IRABI items and thus were questioned similarly about the validity. Other researchers identify Internet addicts with one single self-reported item, for example, asking the participants the extent to which they agree or disagree with the following statement: "I think I might have become a little psychologically dependent on the Internet." Respondents are classified as "Internet dependent" if they chose "agree" or "strongly agree" to the statement (Kubey et al. 2001). This method could be very subjective because the single item only reflects one's self-perceived dependency on Internet without involving any behavioral symptoms of Internet addiction.

In conclusion, different conceptions and measurements of Internet addiction are presented in the literature. There are several observations. First, conceptualizations and definitions of Internet addiction, despite of its variations, basically derive from the diagnostic criteria of substance abuse and pathological gambling in DSM-IV. However, whether Internet addiction should be conceptualized as an impulse control disorder or an addictive disorder is still undetermined. Second, a wide range of assessment tools have been developed while the extent of reliability and validation varies across different measures. Third, clinical usefulness of the measurements has often been questioned. Fourth, the samples on which the instruments were developed were not representative enough. Most of the participants were selected from a particular population (such as university students) and were sometimes self-referred, which inevitably biased the results. Finally, inconsistent criteria have been used in different studies to diagnose Internet addiction, which makes it impossible to make comparison across studies. Therefore, it is the first priority for future researchers to develop a comprehensive definition of Internet addiction that can unify the current diverse conceptualizations and based on which to devise a standardized and psychometrically sound instrument to assess Internet addiction.

Prevalence of Internet Addiction

There are a growing number of prevalence studies on Internet addiction in different parts of the world in which different methodologies were used (Shek et al. 2009). In the United States, a national telephone survey (N = 2,513 adults with a response rate of 56.3%) showed that 5.9% of the respondents suffered from excessive Internet use, 3.7% felt preoccupied by the Internet when off-line, 13.7% found it was difficult to stay away from the Internet for several days at a time, and 12.4% was found to stay online longer than intended very often or often. In the United Kingdom, a study based on 371 randomly selected students showed that 18.3% of the sample was diagnosed as problematic Internet users.

Research studies in the Scandinavian counties suggest that the risk of Internet addiction among young people is increasing. In a study with a sample of 3,237 adolescents from Norway, it was found that 1.98% and 8.68% could be regarded as having Internet addiction and at risk of Internet abuse, respectively. Among the frequent Internet users, which accounted for 49.6% of the whole sample, the percentages of participants classified as Internet addicts and being at risk of Internet abuse rose to 4.02% and 17.66%, respectively. However, in another recent national research in Norway with a random sample of 9,638 individuals aged 16-74 years, only 35 respondents (0.36%) were classified as addictive Internet users. In a study with a sample of 7,292 adolescents from Finland, it was reported that 1.4% of girls and 1.7% of boys were classified as Internet addicts. Among the daily Internet users (26% of the respondents), 4.7% of girls and 4.6% of boys were categorized as Internet addicts.

There were a few Internet addiction prevalence studies conducted in Mediterranean countries. In a study in Turkey (N = 983), 38% of Internet users thought their Internet use might lead to an addiction, compared to 55% who did not. A study in Northern Cyprus showed that 1.1% and 11% of the respondents (N = 686) could be classified as having "pathological usage" and "limited symptoms" (i.e., great risk of pathological Internet usage), respectively. In South Africa, a study was conducted on a sample of university students (N = 1,795) using Young's Diagnostic Questionnaire for Internet addiction and a Problematic Internet Use Questionnaire (PIUQ) adapted from Young's 20-item Internet Addiction Test (IAT). It was shown that the prevalence of Internet addiction ranged from 1.67% to 5.29%, depending on different evaluative criteria used.