East Asian Arch Psychiatry 2010;20:123-32

REVIEW ARTICLE

Dr Kaustav Chakraborty, MD, Drug De-addiction and Treatment Centre, Department of Psychiatry, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Dr Debasish Basu, MD, DNB, MAMS, Drug De-addiction and Treatment Centre, Department of Psychiatry, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Dr KG Vijaya Kumar, MBBS, Drug De-addiction and Treatment Centre, Department of Psychiatry, Postgraduate Institute of Medical Education and< Research, Chandigarh, India.

Address for correspondence: Dr Debasish Basu, PGIMER, Chandigarh 160012, India.
Tel: (91-172) 2706 618; Fax: (91-172) 2744 401; Email: db_sm2002@yahoo.com

Submitted: 25 February 2010; Accepted: 7 July 2010

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Introduction

The Internet is an integral part of modern life for many people. The idea that almost any subjectively rewarding activity (e.g. drug use, shopping, working, running, gambling, using the computer, and using the Internet), which can become the object of addiction, has become increasingly popular.^1-4 Although the earliest reports on the phenomenon of excessive use of the Internet date back to the 1970s, it was not until the early 1990s that reports began to appear in the medical and psychological literature for what Griffiths⁵ called a ‘technological addiction’, described it as a ‘non-chemical addiction involving human-machine interaction’.

Young⁶ was one of the first to describe excessive and problematic Internet use as an addictive disorder. ‘Internet addiction’ is not a recognised diagnostic category in the 10th edition of the International Classification of Diseases (ICD-10) or the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), and thus considerable nosological ambiguity surrounds the phenomenon.⁷ Although much literature is available from abroad, India has been a silent spectator despite its large population and increasing levels of computer and Internet use. Hence, it was worth reviewing the fast-growing literature in this important area wherever it stemmed from.

The data search strategies for this review included electronic databases as well as hand-searches of relevant publications or cross-references from 1970 to 2010. The electronic search included PubMed and other search engines (e.g. Google Scholar and PsychINFO). Cross-searches of electronic and hand-searched key references often yielded other relevant materials. The search terms used, in various combinations, were: ‘Internet’, ‘computer’, ‘addiction’, ‘dependence’, ‘assessment’, ‘scales’, ‘prevalence’, ‘treatment’, ‘co-morbidities’, and ‘correlates’.

Definitions and Proposed Diagnostic Criteria

Although no universally accepted definitions for the condition, investigators seem to agree that it involves problematic computer usage that is time-consuming and causes distress or impairs functioning in important life domains. The many names given to this phenomenon are a testament to the various ways in which it has been perceived. They include: ‘compulsive Internet use’, ‘pathological Internet use’, ‘problematic Internet use’, ‘Internet dependency’, ‘Internet addiction’ and even ‘Internetomania’.⁸ If viewed from an addictive disorder’s perspective, Internet addiction has the following 4 components: (1) excessive use, which is often associated with a loss of a sense of time or a neglect of basic drives; (2) withdrawal, including feelings of anger, tension, and / or depression, when the computer is inaccessible; (3) tolerance, including the need for better computer equipment, more software, or more hours of use; and (4) negative repercussions, including arguments, lying, poor achievement, social isolation, and fatigue.⁹ ‘Internet addiction’ is the most widely used term to describe this maladaptive behaviour. In this article, this term will be used to describe these collective phenomena to avoid further confusion.

Young¹⁰ modified the DSM-IV diagnostic criteria for pathological gambling to construct diagnostic criteria for pathological Internet use, which she defined as 5 or more of 8 characteristic symptoms present in the preceding 6 months. She further divided Internet addiction into 5 subtypes depending on the particular component of use to which it was directed addiction, namely: (1) cybersexual addiction; (2) cyber-relational addiction; (3) net compulsions; (4) information overload; and (5) computer addiction.¹¹ Young¹⁰ also found that email, chat, and the web are examples of applications used on the Internet, whose nature has addictive properties. Moreover, interactive ‘real-time’ services such as Internet relay chat and multi-user domains proved to be most addictive.

Shapira et al¹² defined problematic Internet use as uncontrollable, markedly distressing, time-consuming or resulting in social, occupational, or financial difficulties, and not solely present as a manifestation of hypomanic and manic symptoms. Later, Shapira et al¹³ conceptualised Internet addiction as an impulse control disorder (ICD) and proposed the diagnostic criteria of problematic Internet use to be based on the general style of ICDs in the Text Revision of the DSM-IV. Aboujaoude et al¹⁴ developed 4 sets of diagnostic criteria, which were created from diagnostic criteria of other ICDs (obsessive-compulsive disorder and substance abuse) and then suggested criteria for problematic Internet use.

Very recently, Tao et al¹⁵ proposed formal diagnostic criteria for Internet addiction disorder (IAD). These were listed as follows. Criterion (a) or the symptom criterion entailed 7 clinical symptoms of IAD, of which 2 (preoccupation with Internet use and withdrawal phenomena) along with at least 1 of the remaining 5 had to be satisfied [what the authors call the “2+1 rule”]). Criterion (b) referred to clinically significant impairment (functional and psychosocial impairments). Criterion (c) dealt with the disorder’s course (duration of addiction lasting at least 3 months, with at least 6 hours of non-essential Internet usage per day). Criterion (d) dealt with exclusions (e.g. dependency attributed to psychotic disorders). Using a series of statistical analyses, they demonstrated excellent inter-rater reliability, diagnostic accuracy, and specificity for their diagnostic criteria.

Aetiological Models

Various aetiological models have been proposed to understand Internet addiction. ‘Learning theory’ emphasises the positive reinforcing effects of Internet use, which can induce feelings of well-being and euphoria in the user, and works on the principle of operant conditioning.¹⁶ Further, Internet use by a shy or anxious individual to avoid anxiety-provoking situations such as a face-to-face interaction tend to reinforce use by avoidance conditioning. Yet why so few and not everybody using the Internet develop Internet addiction remains unclear. In this context it may be worth studying the temperament of predisposed individuals.

Davis¹⁷ proposed a ‘cognitive behavioural theory’ of problematic Internet use, which he viewed as arising from a unique pattern of Internet-related cognitions and behaviours. Examples of maladaptive cognitions include self-doubt, self-focused rumination, low self-efficacy and negative self- appraisals. Although interesting at a theoretical level, this hypothesis needs to be proven through systematic research.

Caplan¹⁸ has developed an explanatory theory invoking ‘deficient social skills’. His first assumption was that lonely and depressed individuals hold negative views of their social competence. The second assumption was that there are several features of computer-mediated communications that are particularly attractive to persons who see themselves as low in social competence. In this context, computer-mediated communication interactions give people greater flexibility in self-presentation than face-to-face communication, which facilitates omission or editing of information regarded as negative or harmful. As Morahan-Martin and Schumacher¹⁹ put it, “The Internet can be socially liberating — the Prozac of social communication”. Although this theory attempts to explain Internet addiction in a subgroup of people, it cannot account for the whole phenomenon.

The ‘reward-deficiency hypothesis’ suggests that those who achieve less satisfaction from natural rewards (food, water, sex) turn to substances to seek enhanced stimulation from reward pathways.²⁰ Internet use provides of a drug, Internet use provides immediate reward with minimal delay, mimicking the stimulation provided by alcohol or drugs. Impulsivity is seen as a risk factor for the development of addiction.Shaffer²¹ has suggested that Internet use is linked to sensation-seeking behaviour, which is a sub-trait of impulsivity. Neurobiological research aimed at finding the neural substrates / pathways that can be useful to establish the causal link.

Ongoing research into various aspects of Internet addiction, coupled with the fields of genetics and neurobiology have also contributed to this topic. Recently, genetic polymorphisms of the serotonin transporter gene (SS-
5HTTLPR) have been found in excessive Internet users.²² However, in view of association of this polymorphism with a number of other psychiatric conditions (e.g. mood disorders, anxiety disorders, alcoholism, nicotine dependence), this finding needs replication in a well-controlled population. A voxel-based morphometry study by Zhou et al²³ found that adolescent Internet addicts had lower grey matter density in the left anterior cingulate cortex, left posterior cingulate cortex, left insula, and left lingual gyrus, compared with healthy controls. They suggested that this may provide a new insight into the pathogenesis of Internet addiction, especially in light of deficits in decision-making function and strategy learning lag.²⁴ Functional neuroimaging studies with provocation techniques can be useful for this purpose. From the above discussion, it is evident that none of the theories is self-explanatory and a combination of them may help us understand this complex phenomenon to some extent.

Controversies regarding Internet Addiction

Under typical circumstances, the Internet should not be considered the source of gambling or an object of addiction.²⁵ Despite the above-mentioned aetiological models, it is still not clear precisely what Internet addicts become addicted to. The possibilities suggested are: the process of typing, the Internet as a medium for communication, and the Internet as a source of information. Particular applications (e.g. email, gambling, video games, pornography and multi-user domains / dungeons) can be enjoyed with the anonymity of the Internet.^26,27 Critics of Internet addiction as a discrete disorder point out that the Internet is merely a communications medium — not a substance. Thus it merely fills a pathological need to play a game or view pornography and therefore merely represents a means to fulfilling an underlying psychopathology that would be manifested in some other way, were it not available.

When the concept of Internet addiction was first introduced in a pioneer study by Young,²⁸ it sparked a debate among both clinicians and academicians. Part of the controversy revolved around the contention that only physical substances ingested into the body could be termed ‘addictive’. While many believed the term ‘addiction’ should be applied only to instances involving the ingestion of a drug,^29,30 defining addiction has moved beyond this to include a number of behaviours not involving an intoxicant, such as: compulsive gambling,³¹ video-game playing,³² overeating,³³ exercise,³⁴ love relationships,³⁵ and television- viewing.³⁶

Internet addiction has been thought of as a compulsive-impulsive spectrum disorder.³⁷ However, Pies³⁸ contends that withdrawal and tolerance have not been established in Internet addiction subjects using physiological measures comparable to those used in patients dependent on various substances. As per Pies,³⁸ these terms have been used either metaphorically or to describe coarse behavioural criteria, such as the patient’s complaints of feeling irritable or anxious. He also emphasised that there was no universal agreement as to specific diagnostic criteria for Internet addiction. Nor was it clear whether it is a discrete mental disorder, or, indeed, whether it is a disorder at all.³⁸ Similar concerns have been raised by others.³⁹ According to Pies, a less emotionally loaded and more encompassing term than ‘Internet addiction’ is what he terms as ‘pathological use of electronic media (PUEM)’. He does not suggest PUEM as a discrete diagnosis for the present; however, he does suggest “a detailed description of PUEM should be added to the DSM-V appendix, as a ‘condition for further study’”.³⁸ He further hints that PUEM-like symptoms be classified as “impulse control disorder not otherwise specified (NOS)” under the current DSM-IV system, rather than as an addictive disorder. While appreciating Pies’ fairly balanced critique, we feel that both his suggestions (of PUEM rather than Internet addiction, and lumping it under ICD NOS rather than addictions) are premature and that only future studies can clarify the issues. We agree with him, however, that the condition deserves further rigorous, systematic, and unbiased study and that it cannot simply be wished away.

Furthermore, the issue of psychiatric co-morbidity raises other diagnostic dilemmas. A high prevalence of co-morbid depressive and anxiety disorders along with a low prevalence of substance-related problems have raised doubts as to whether Internet addiction may be a symptom of Axis I or Axis II disorders, particularly in adolescents.^40,41

A constellation of related signs and symptoms — essentially, a syndrome — may ultimately be understood as a specific disease entity when at least one of the following criteria are met: (i) a pattern of genetic transmission is discovered, sometimes leading to the identification of a specific genetic locus; (ii) the syndrome’s aetiology, pathophysiology and / or pathologic anatomy become reasonably well understood; and (iii) the syndrome’s course, prognosis, stability, and response to treatment are seen to be relatively predictable and consistent across many different populations.^42,43 Notwithstanding the huge amount of research emerging mainly from Asia and the United States, there is a worry that creating a separate category for Internet addiction will open the door to all kinds of new ‘disease’ categories, as new technologies develop (e.g. iPhone addiction, mobile addiction, virtual reality addiction). Expanding an already mushrooming catalogue of supposed ‘disorders’ requires caution, lest it undermines the public’s trust in psychiatric diagnosis.^38,39 Table 1 summarises the various pros and cons of the proposed definitions, symptoms and subtypes, diagnoses, and aetiologies.

Epidemiology

There have been various community and online surveys to estimate the prevalence of Internet addiction, with little uniformity of the definitions employed or assessment methods.⁴⁴ The studies have predominantly focused on younger populations rather than the wider adult population. This perhaps reflects the view that this is primarily a disorder of younger persons. In studies that focus on younger people, prevalence estimates range from 0.9 to 38%.^45,46 Interestingly, the 4 online surveys produced prevalence estimates ranging from 3.5 to 18%.^47-50 The reasons for such huge variability could be: difficulty in conceptualising Internet addiction, lack of availability of standard diagnostic criteria, heterogeneity of the populations studied, and failure to consider psychiatric co-morbidity in some of the studies (Table 2).^14,19,45-57

Based on data from the community, online surveys, as well as clinical samples, Internet addiction appears to have a male preponderance.^{19,45,48,53-55} Regarding age of onset, studies have found that the disorder manifests itself in the late 20s or early 30s.^11,58 Black et al⁵⁸ reported that their subjects were introduced to computers at a mean age of 17 years; there was a lag time of 11 years from initial computer use to problematic computer use, and it led to a deficit in general mental health (as reflected by testing with the Short Form-36 health survey).⁵⁹

Assessment of Internet Addiction

Symptoms of Internet addiction may not always be revealed in an initial clinical interview; it is therefore important that clinicians routinely assess for its presence. Four specific cues need to be explored, viz: applications; emotions; cognitions; and life events which often trigger Internet use or ‘Net binges’.⁶⁰ Several screening and assessment instruments have been developed to assess Internet addiction, although none has emerged as the ‘gold standard’.^{9,10,27,50,61-68}

The above-mentioned screening and diagnostic instruments have severe limitations in terms of applicability. First, they are based on different theoretical frameworks, so there is limited agreement about their crucial components, or dimensions. Second, most are self-reported instruments and hence dependent on the respondent answering questions honestly, yet none incorporate a ‘lie scale’ to correct for this. Third, none of them identify specific Internet applications (e.g. chat rooms, email, pornography) to which the user might be addicted.⁶⁹ Hence, it is advisable to rely heavily on the clinical interview and use diagnostic tools only within a comprehensive framework.

Clinical Manifestations

Studies have attempted to delineate the behaviour of problematic Internet users. Shotton⁷⁰ found that, compared with 2 normative groups, addicts spent significantly more time using their computers at home and at work, and found it difficult to stop ‘computing’ and in the process lost all sense of time. Egger and Rauterberg⁵⁰ also found that Internet addicts developed urges to use the Internet when offline, and even felt guilty or depressed when spending too much time online and recognised its negative consequences.

Black et al⁵⁸ systematically assessed the experiences of 21 compulsive computer users. Most admitted that their computer usage had caused problems with family or friends, or with work or school. Nearly one-third had tried to cut back, but observed that doing so made them more anxious.

In a study of 596 subjects that 396 of whom were considered computer-dependent, Young⁶ observed that ‘dependents’ predominately used the 2-way communication functions on the Internet, such as chat rooms, multi-user dungeons, newsgroups or emails, while non-dependents tended to use information-seeking aspects of the Internet and email. Computer dependents reported that their excessive Internet use resulted in personal, family and occupational difficulties, with more than 50% rating these problems as ‘severe’.

A recently conducted study from Chandigarh, India found that about 59% of respondents would get upset when the Internet was not available, 54% felt the need to use Internet every day, 45% lost track of time after starting to surf, and 43% stayed online longer than originally intended.⁷¹ Another Indian study has found that compared with non-dependent subjects, those who were dependent on the Internet would delay their work to spend time online, lose sleep due to late-night log-ons, feel lonelier and feel life would be boring without the Internet.⁷² Although the above-mentioned studies attempted to tap the different dimensions of Internet use, whether such reactions should be labelled as pathological remains controversial. All these studies were limited by lack of standardised criteria for Internet addiction, not taking any account about the subject’s Internet use from relatives’, and failure to apply stringent disability criteria.

Co-morbidities of Internet Addiction

Studies suggest that Internet addiction is frequently associated with DSM-IV Axis I and Axis II disorders. Black et al⁵⁸ found that nearly 30% of the subjects in their study met the criteria for a current disorder; the most common being disorders of mood (24%), anxiety (19%), substance use (14%), and psychoses (10%). Nearly half of the subjects met the criteria for a lifetime psychiatric disorders, including for substance use (38%), mood (33%), anxiety (19%) and psychotic symptoms (14%). Various ICDs were also conspicuous by their presence; 38% of the subjects had at least 1 ICD (compulsive buying, 19%). Besides, 52% of Internet addicts met criteria for at least 1 personality disorder, the most frequent being borderline, antisocial, and narcissistic disorders.

Shapira et al¹² reported DSM-IV Axis I diagnosis in addition to their problematic Internet use in all 20 of the subjects they assessed. In all, 70% met the criteria for a current bipolar disorder and the figure jumped to 80% when a lifetime diagnosis was considered. They also noted that 35% of their subjects met the criteria for an ICD, including intermittent explosive disorder (10%), kleptomania (5%), pathological gambling (5%), and compulsive buying (20%).

Increased use of the Internet was associated with higher ratings on measures of depression, loneliness and social isolation.^73,74 In other studies, a high mean score on the Beck Depression Inventory was also found among Internet addicts.^75,76 A recent study⁷⁷ found attention-deficit / hyperactivity disorder (14%), hypomania (7%), generalised anxiety disorder (15%), social anxiety disorder (15%), dysthymia (7%), obsessive compulsive personality disorder (7%), borderline personality disorder (14%), and avoidant personality disorder (7%) to be associated co-morbidities. The same study also found that Internet addicts had higher mean score on the Dissociative Experience Scale, suggesting that dissociative symptoms were related to the severity and impact of Internet addiction. Another recent study⁷⁸ noted an association between Internet addiction and harmful alcohol use.

Based on the above findings, it is still unclear whether Internet addiction should be considered a discrete disorder. Critics of Internet addiction argue that excessive use of the Internet is a secondary manifestation of underlying Axis I or Axis II disorders and may represent adaptive ‘self- soothing’ or a form of avoidance of interpersonal discomfort associated with these underlying conditions.

Consequences and Correlates of Internet Addiction

Despite its positive uses, excessive Internet use to the point of addiction can have wide-ranging adverse consequences that affect many domains of an individual’s life, including: interpersonal, social, occupational, psychological, and physical.^7,79

The scope of relationship problems caused by Internet addiction has been undermined by its current popularity and advanced utility. Young²⁸ found that serious relationship problems were reported by 53% of Internet addicts surveyed. Marriages appear to be the most affected as Internet use interferes with responsibilities and obligations at home, and it is typically the spouse who takes on these neglected chores and often feels like a ‘cyberwidow’.⁸⁰ Matrimonial lawyers have reported seeing a rise in divorce cases due to ‘cyberaffairs’.⁸¹

Employers have found that employees with access to the Internet at their desks spend a considerable amount of the working day engaged in non–work-related Internet use.⁸² Internet addiction can lead to poor academic performance in school and college and impaired functioning at work.^83,84 There is even a case report of cardiac arrest leading to death in an Internet addict after an Internet gaming binge, during which the subject neither ate nor slept.⁸⁵

Various studies have attempted to predict Internet addiction by finding its correlates. Much attention has been paid to the predictive value of personality characteristics for Internet addiction. Evidently, high novelty seeking, high harm avoidance, and low reward dependence behaviour predict a high proportion of adolescents with Internet addiction.⁸⁶ A recent study⁸⁷ carried out among Turkish university students reported that loneliness, depression, and computer self-efficacy were significant predictors of problematic Internet use. A Finnish study⁸⁸ found that the severity of Internet addiction (as measured by an Internet Addiction Test) yielded a significant negative correlation with social support and a significant positive correlation with the CAGE score. A study among adolescents by Lam et al⁸⁹ identified male gender, drinking, family dissatisfaction, and experience of recent stressful events as potential risk factors. A prospective study⁹⁰ among adolescents found that depression, attention-deficit / hyperactivity disorder, social phobia, and hostility predicted the occurrence of Internet addiction in the 2-year follow-up. Among these, hostility and attention-deficit / hyperactivity disorder were the most significant predictors of Internet addiction in male and female adolescents, respectively. A survey of university freshman in Taiwan⁹¹ found a positive relationship between Internet addiction and male gender, neuroticism scores and the Chinese Health Questionnaire–12 score.

Management

Although there are no evidence-based treatments for Internet addiction, both psychotropic medication and psychotherapy have been recommended (Table 3). There is general agreement that one should be cautious in diagnosing Internet addiction, but those who are diagnosed should receive the benefit of whatever therapy is available.

There are small, open-label studies⁹² and case reports⁹³ claiming benefits by escitalopram, other antidepressants, or mood stabilisers. Recently, Bostwick and Bucci⁹⁴ reported a case of Internet sex addiction that did not respond to prescribed antidepressants, psychotherapy (individual and group), or participation in sexual addicts anonymous. Significant improvement only ensued when the opiate antagonist, naltrexone, was added to ongoing sertraline therapy. In a shocking development, CCTV-12, a central government channel, ran a series of glowing reports on a clinic in Shandong Province in eastern China that used electric shocks on Internet addicts, as part of what the clinic’s director has called a ‘holy crusade’ to cure Internet addiction.⁹⁵ Given the Internet’s numerous advantages and positive uses in day-to-day life, it is impractical to advocate total abstinence (as might be done for substance abuse). The guiding principle should be ‘moderate and controlled use’.⁷

Cognitive behavioural therapy has been modified to treat Internet addiction. Hall and Parsons⁹⁶ observed that these techniques are familiar to many mental health treatment providers and can apply to treating not only substance misuse but also ‘nonchemical addictions’, including Internet addiction. Young⁹⁷ has recently developed a guide, which employs cognitive behavioural techniques, for therapists working with Internet addicts. This suggests the following exercises to achieve abstinence from problematic Internet use: (i) practising the opposite behaviour; (ii) using external stoppers (e.g. a timer signalling when the session should end); (iii) setting time limits; (iv) setting task priorities to aid in Internet goals during each Internet session; (v) using reminder cards (posted on the computer) with a list of the 5 major problems caused by the Internet addiction, and a parallel list of the 5 major benefits of cutting down Internet use; and (vi) taking a personal inventory, whereby the therapist helps the client cultivate alternative activities that take him / her away from the computer. A study⁹⁸ evaluating the efficacy of cognitive behaviour therapy for Internet addicts indicates that the majority of subjects were able to manage their presenting complaints by the eighth session and symptom management was sustained at the 6-month follow-up. Self-help books and tapes are available online and may be helpful to some Internet addicts.⁶ Internet addiction is likely to disrupt family relationships. If it does, family intervention should be part of that individual’s treatment.⁷ Marriage (or couple) counselling may be helpful when one member of the dyad has disrupted the relationship. In China there is even a halfway house for adolescents with Internet addiction; the length of stay is from 10 to 14 days and available treatments include: group therapy, medication, acupuncture, and sports.⁹⁹

In the past decade, much interest has been generated regarding Internet addiction. Studies have started pouring in from different parts of the world, generating important data making it impossible to ignore the problem anymore. Yet the concept of Internet addiction as a distinct psychiatric disorder is still in its infancy. Lack of conceptual clarity has hindered the development of proper assessment tools and epidemiological research on the topic.

Thus, as of today, the American Psychiatric Association recommendation to include Internet addiction in its forthcoming DSM-V (but only as an appendix and not in the main body of recognised addictive disorders) appears a fairly balanced and cautious approach. Hopefully, this could give rise to more meaningful research on this important but controversial area.^100,101 Understandably, this has made news, and very recently has been cited by Science in its ‘News of the Week’ section.¹⁰²

References

1. Shaffer HJ. The most important unresolved issue in the addictions: conceptual chaos. Subst Use Misuse 1997;32:1573-80.
2. Shaffer HJ. Strange bedfellows: a critical view of pathological gambling and addiction. Addiction 1999;94:1445-8.
3. The dope chronicles: 1850-1950. In: Silver G, editor. San Francisco: Harper & Row; 1979.
4. US Census Bureau. Computer and Internet use in the United States: Washington, DC: US Department of Commerce, Economics and Statistics Administration, US Census Bureau; 2005.
5. Griffiths M. Gambling on the Internet: a brief note. J Gambl Stud 1996;12:471-3.
6. Young KS. Caught in the net: how to recognize the signs of Internet addiction — and a winning strategy for recovery. New York: John Wiley & Sons, Inc; 1998.
7. Murali V, George S. Lost online: an overview of Internet addiction. Adv Psychiatr Treat 2007;13:24-30.
8. Shaw M, Black DW. Internet addiction: definition, assessment, epidemiology and clinical management. CNS Drugs 2008;22:353-65.
9. Beard KW, Wolf EM. Modification in the proposed diagnostic criteria for Internet addiction. Cyberpsychol Behav 2001;4:377-83.
10. Young K. Internet addiction: the emergence of a new clinical disorder. Cyberpsychol Behav 1996;3:237-44.
11. Young K, Pistner M, O’Mara J, Buchanan J. Cyber-disorders: the mental health concern for the new millennium. Cyberpsychol Behav 1999;2:475-9.
12. Shapira N, Goldsmith T, Keck Jr P, Khosla UM, McElroy SL. Psychiatric features of problematic Internet use. J Affect Disord 2000;57:267-72.
13. Shapira NA, Lessig MC, Goldsmith TD, Szabo ST, Lazoritz M, Gold MS, et al. Problematic Internet use: proposed classification and diagnostic criteria. Depress Anxiety 2003;17:207-16.
14. Aboujaoude E, Koran LM, Gamel N, Large MD, Serpe RT. Potential markers for problematic Internet use: a telephone survey of 2,513 adults. CNS Spectr 2006;11:750-5.
15. Tao R, Huang X, Wang J, Zhang H, Zhang Y, Li M. Proposed diagnostic criteria for Internet addiction. Addiction 2010;105:556-64.
16. Wallace P. The Psychology of the Internet. New York: Cambridge University Press; 1999.
17. Davis RA. A cognitive-behavioural model of pathological Internet use. Comput Human Behav 2001;17:187-95.
18. Caplan SE. Preference for online social interaction: a theory of problematic Internet use and psychosocial well-being. Comm Research 2003;30:625-48.
19. Morahan-Martin J, Schumacher P. Incidence and correlates of pathological Internet use among college students. Comput Human Behav 2000;16:13-29.
20. Blum K, Cull JG, Comings ED. Biogenetics of reward deficiency syndrome. Sci Am 1996;84:132-45.
21. Shaffer HJ. Understanding the means and objects of addiction: technology, the Internet, and gambling. J Gambl Stud 1996;12:461-9.
22. Lee YS, Han DH, Yang KC, Daniels MA, Na C, Kee BS, et al. Depression like characteristics of 5HTTLPR polymorphism and temperament in excessive Internet users. J Affect Disord 2008;109:165- 9.
23. Zhou Y, Lin FC, Du YS, Qin LD, Zhao ZM, Xu JR, et al. Gray matter abnormalities in Internet addiction: a voxel-based morphometry study. Eur J Radiol 2009 Nov 17. Epub ahead of print.
24. Sun DL, Chen ZJ, Ma N, Zhang XC, Fu XM, Zhang DR. Decision- making and prepotent response inhibition functions in excessive Internet users. CNS Spectr 2009;14:75-81.
25. Shaffer HJ, Hall MN, Vander Bilt J. “Computer addiction”: a critical consideration. Am J Orthopsychiatry 2000;70:162-8.
26. Griffiths M. Internet addiction: does it really exist? In: Gackenbach J, editor. Psychology and the Internet. Academic Press; 1998: 61-75.
27. Caplan SE. Problematic Internet use and psychosocial well-being: development of a theory-based cognitive-behavioral measurement instrument. Comput Human Behav 2002;18:553-75.
28. Young KS. Internet addiction: the emergence of a new clinical disorder. Cyberpsychol Behav 1998;1:237-44.
29. Rachlin H. Why do people gamble and keep gambling despite heavy losses? Psychol Sci 1990;1:294-7.
30. Walker MB. Some problems with the concept of “gambling addiction”: should theories of addiction be generalized to include excessive gambling? J Gambl Behav 1989;5:179-200.
31. Griffiths M. The cognitive psychology of gambling. J Gambl Stud 1990;6:31-42.
32. Keepers GA. Pathological preoccupation with video games. J Am Acad Child Adolesc Psychiatry 1990;29:49-50.
33. Lesieur HR, Blume SB. Pathological gambling, eating disorders, and the psychoactive substance use disorders. J Addict Dis 1993;12:89- 102.
34. Morgan W. Negative addiction in runners. Phys Sportsmed 1979;7:57- 70.
35. Peele S, Brodsky A. Love and addiction. Scarborough, Ontario: New American Library of Canada; 1979.
36. Winn M. The plug-in drug. New York, NY: Viking Penguin, Inc; 1977.
37. Block JJ. Issues for DSM-V: internet addiction. Am J Psychiatry 2008;165:306-7.
38. Pies R. Should DSM-V designate “Internet Addiction” a mental disorder? Psychiatry (Edgemont) 2009;6:31-7.
39. Swaminath G. Internet addiction disorder: fact or fad? Nosing into nosology. Indian J Psychiatry 2008;50:158-60.
40. Ha JH, Yoo HJ, Cho IH, Chin B, Shin D, Kim JH. Psychiatric comorbidity assessed in Korean children and adolescents who screen positive for Internet addiction. J Clin Psychiatry 2006;67:821-6.
41. Kratzer S, Hegerl U. Is “Internet Addiction” a disorder of its own? A study on subjects with excessive Internet use [in German]. Psychiatr Prax 2008;35:80-3.
42. Pies R. Beyond reliability: biomarkers and validity in psychiatry. Psychiatry (Edgemont) 2008;5:48-52.
43. McHugh PR, Slavney PR. The perspectives of psychiatry. Baltimore, MD: Johns Hopkins University Press; 1986.
44. Petersen KU, Weymann N, Schelb Y, Thiel R, Thomasius R. Pathological Internet use — epidemiology, diagnostics, co-occurring disorders and treatment. Fortschr Neurol Psychiatr 2009;77:263-71.
45. Yoo HJ, Cho SC, Ha J, Yune SK, Kim SJ, Hwang J, et al. Attention deficit hyperactivity symptoms and Internet addiction. Psychiatry Clin Neurosci 2004;58:487-94.
46. Leung L. Net-generation attributes and seductive properties of the Internet as predictors of online activities and Internet addiction. Cyberpsychcol Behav 2004;7:333-48.
47. Whang LS, Lee S, Chang G. Internet over-users’ psychological profiles: a behavior sampling analysis on Internet addiction. Cyberpsychol Behav 2003;6:143-50.
48. Niemz K, Griffiths M, Banyard P. Prevalence of pathological Internet use among university students and correlations with self-esteem, the General Health Questionnaire (GHQ) and disinhibition. Cyberpsychol Behav 2005;8:562-70.
49. Greenfield DN. Psychological characteristics of compulsive Internet use: a preliminary analysis. Cyberpsychol Behav 1999;2:403-12.
50. Egger O, Rauterberg M. Internet behavior and addiction. Zurich: Swiss Federal Institute of Technology; 1996.
51. Jang KS, Hwang SY, Choi JY. Internet addiction and psychiatric symptoms among Korean adolescents. J Sch Health 2008;78:165-71.
52. Ghassemzadeh L, Shahraray M, Moradi A. Prevalence of Internet addiction and comparison of Internet addicts and non-addicts in Iranian high schools. Cyberpsychol Behav 2008;11:731-3.
53. Chou C, Hsiao MC. Internet addiction, usage, gratification, and pleasure experience: the Taiwan college students’ case. Comput Educ 2000;35:65-80.
54. Kaltiala-Heino R, Lintonen T, Rimpela A. Internet addiction? Potentially problematic use of the Internet in a population of 12-18 year old adolescents. Addict Res Theory 2004;12:89-96.
55. Johansson A, Gotestam K. Internet addiction: characteristics of a questionnaire and prevalence in Norwegian youth (12-18 years). Scand J Psych 2004;45:223-9.
56. Kim K, Ryu E, Chon MY, Yeun EJ, Choi SY, Seo JS, et al. Internet addiction in Korean adolescents and its relationship to depression and suicidal ideation: a questionnaire survey. Int J Nurs Stud 2006;43:185- 92.
57. Pallanti S, Bernardi S Leonardo Q. The shorter PROMIS questionnaire and the internet addiction scale in the assessment of multiple addictions in a high-school population: prevalence and related disability. CNS Spectr 2006;11:966-74.
58. Black DW, Belsare G, Schlosser S. Clinical features, psychiatric comorbidity, and health-related quality of life in persons reporting compulsive computer use behavior. J Clin Psychiatry 1999;60:839-44.
59. Ware J. Appendix C: Script for personal interview SF-36 administration. In: Ware J, editor. SF-36 health survey manuals and interpretations. Boston (MA): Nimrod Press; 1993.
60. Young KS. Internet addiction: symptoms, evaluation and treatment. In: Van de Creek L, Jackson T, editors. Innovations in clinical practice: a source book. Professional Resource Press; 1999: 19-31.
61. Brenner V. Psychology of computer use: XLVII. Parameters of Internet use, abuse and addiction: the first 90 days of the Internet Usage Survey. Psychol Rep 1997;80:879-82.
62. Davis RA, Flett GL, Besser A. Validation of a new scale for measuring problematic Internet use: implications for pre-employment screening. Cyberpsychol Behav 2002;5:331-45.
63. Chen SH, Weng LC, Su YJ, Wu HM, Yang PF. Development of Chinese Internet Addiction Scale and its psychometric study. Chin J Psychol 2003;45:279-94.
64. Clark DJ, Frith KH, Demi AS. The physical, behavioural, and psychosocial consequences of Internet use in college students. Comput Inform Nurs 2004;22:153-61.
65. Nichols LA, Nicki R. Development of a psychometrically sound Internet addiction scale: a preliminary step. Psychol Addict Behav 2004;18:381-4.
66. Ko CH, Yen JY, Chen CC, Chen SH, Yen CF. Proposed diagnostic criteria of Internet addiction for adolescents. J Nerv Ment Dis 2005;193:728-33.
67. Ko CH, Yen JY, Chen SH, Yang MJ, Lin HC, Yen CF. Proposed diagnostic criteria and the screening and diagnosing tool of Internet addiction in college students. Compr Psychiatry 2009;50:378-84.
68. Demetrovics Z, Szeredi B, Rózsa S. The three-factor model of Internet addiction: the development of the Problematic Internet Use Questionnaire. Behav Res Methods 2008;40:563-74.
69. Beard KW. Internet addiction: a review of current assessment techniques and potential assessment questions. Cyberpsychol Behav 2005;8:7-14.
70. Shotton MA. The costs and benefits of ‘computer addiction’. Behav Inform Tech 1991;10:219-30.
71. Chakraborty K, Grover S, Basu D. Pattern of Internet use: a survey [Abstract]. Indian J Psychiatry 2010;52:S42.
72. Nalwa K, Anand AP. Internet addiction in students: a cause of concern. Cyberpsychol Behav 2003;6:653-6.
73. Kraut R, Patterson ML, Landmark V, Kiesler S, Mukopadhyay T Scherlis W. Internet paradox: a social technology that reduces social involvement and psychological well being? Am Psychol 1998;53:1017- 31.
74. Nie NH, Erbring L. Internet and society: a preliminary report. Stanford Institute for the Quantitative Study of Society website: http://www.stanford.edu/group/siqss/Press_Release/press_release.html. Accessed 26 May 2010.
75. Young KS, Rodgers RC. The relationship between depression and Internet addiction. Cyberpsychol Behav 1998;1:25-8.
76. Petrie H, Gunn D. Internet “addiction”: the effects of sex, age, depression and introversion. Presented at the British Psychological Society London Conference; 1998 Dec 15-16; London.
77. Bernardi S, Pallanti S. Internet addiction: a descriptive clinical study focusing on comorbidities and dissociative symptoms. Compr Psychiatry 2009;50:510-6.
78. Yen JY, Ko CH, Yen CF, Chen CS, Chen CC. The association between harmful alcohol use and Internet addiction among college students: comparison of personality. Psychiatry Clin Neurosci 2009;63:218-24.
79. Guan SS, Subrahmanyam K. Youth Internet use: risks and opportunities. Curr Opin Psychiatry 2009;22:351-6.
80. Kwiatkowska A, Ziolko E, Krysta K, Muc-Wierzgon M, Krupka- Matuszczyk I. Impact of Internet abuse on human relationships. Eur Psychiatry 2007;22:S192.
81. Quittner J. Divorce Internet style. Time 1997 Apr 14:72.
82. Beard K. Internet addiction. Current status and implications for employees. J Employ Couns 2002;39:2-11.
83. Murphey B. Computer addictions entangle students. APA Monitor 1996;27:38-9.
84. Surf’s up! Is productivity down? Robert Half International 1996 Oct 10:1.
85. Christakis DA, Moreno MA. Trapped in the Net. Will Internet addiction become a 21st-century epidemic? Arch Pediatr Adolesc Med 2009;163:959-60.
86. Ko CH, Yen JY, Chen CC, Chen SH, Wu K, Yen CF. Tridimensional personality of adolescents with Internet addiction and substance use experience. Can J Psychiatry 2006;51:887-94.
87. Ceyhan AA, Ceyhan E. Loneliness, depression, and computer self- efficacy as predictors of problematic Internet use. Cyberpsychology Behav 2008;11:699-701.
88. Korkeila J, Kaarlas S, Jääskeläinen M, Vahlberg T, Taiminen T. Attached to the web — harmful use of the Internet and its correlates. Eur Psychiatry 2009;25:236-41.
89. Lam LT, Peng ZW, Mai JC, Jing J. Factors associated with Internet addiction among adolescents. Cyberpsychol Behav 2009;12:551-5.
90. Ko CH, Yen JY, Chen CS, Yeh YC, Yen CF. Predictive values of psychiatric symptoms for Internet addiction in adolescents. Arch Pediatr Adolesc Med 2009;163:937-43.
91. Tsai HF, Cheng SH, Yeh TL, Shih CC, Chen KC, Yang YC, et al. The risk factors of Internet addiction — a survey of university freshmen. Psychiatry Res 2009;167:294-9.
92. Hadley SJ, Baker BR, Hollander E. Efficacy of escitalopram in the treatment of compulsive-impulsive computer use disorder (abstract). Biol Psychiatry 2006;59:261S.
93. Sattar P, Ramaswamy S. Internet gaming addiction. Can J Psychiatry 2004;49:869-70.
94. Bostwick JM, Bucci JA. Internet sex addiction treated with naltrexone. Mayo Clin Proc 2008;83:226-30.
95. Stone R. Science in society. China reins in wilder impulses in treatment of ‘Internet addiction’. Science 2009;324:1630-1.
96. Hall AS, Parsons J. Internet addiction: college student case study using best practices in cognitive behavior therapy. J Ment Health Couns 2001;23:312-27.
97. Young K. A therapist’s guide to assess and treat Internet addiction. Website : http://www.keithadkins.com/netaddiction/articles/practitioners.pdf. Accessed 26 May 2010.
98. Young KS. Treatment outcomes with Internet addicts. Cyberpsychol Behav 2007;10:671-9.
99. Ang A. China takes unique steps to combat web addiction. USA Today; 2005 Jul 1. Website: http://www.usatoday.com/tech/news/2005-07-01-china-web-addiction_x.htm. Accessed 26 May 2010.
100. DSM-5 Development, American Psychiatric Association. Substance- related disorders. Website: http://www.dsm5.org/ProposedRevisions/Pages/Substance-RelatedDisorders.aspx. Accessed 26 May 2010.
101. O’Brien CP. Commentary on Tao et al. (2010): internet addiction and DSM-V. Addiction 2010;105:565.
102. Holden C. Psychiatry. Behavioral addictions debut in proposed DSM-V. Science 2010;327:935.