Internet addiction is a phenomenon unknown before the mid-1980s. The term was first coined by the psychologist Ivan Goldberg in the United States, who proposed it as a disorder in a satirical hoax in 1995. However, empirical evidence indicates that Internet addiction, with common features similar to other addictive disorders, does appear to exist for some Internet users. Since the early studies conducted by the pioneer and leading proponents, such as Kimberly Young and Mark Griffiths, Internet addiction has received attention from multiple disciplines ranging from social psychology, public health, education, and social work to communication. Research on Internet addiction has proliferated, addressing topics as diverse as definition, classification, epidemiology, assessment, and diagnosis, as well as treatment and prevention. Nowadays, Internet addiction has undergone a remarkable metamorphosis from psychiatric curiosity to a publicly recognized health risk. As public and professional awareness of Internet addiction is raised, it becomes increasingly important to understand, assess, and treat this phenomenon. Many societies have witnessed an increasing number of treatments and clinics coping with this new plight.

Internet addiction is considered to be a broad term covering a wide variety of Internet activities, usually including online gaming, online relationships, cybersex, and information gathering. Internet addiction is characterized by excessive or uncontrolled preoccupations, urges, or behaviors regarding Internet use that leads to impairment and distress. However, there are different definitions available for the phenomenon. Some researchers have adapted substance use disorder, but others use pathological gambling as diagnosed by the Diagnostic and Statistical Manual of Page 742  |  Top of ArticleMental Disorders, fourth edition (DSM-IV) as a reference, which results in an inconsistent definition of Internet addiction. Diagnostic instruments have been developed to screen Internet addiction. Still, there has not been a universally accepted gold standard assessment or diagnostic tool. At present, the diagnosis of Internet addiction is based on observations, counseling interviews, or criteria proposed by different researchers.

Internet addiction is associated with large amounts of time spent on Internet activities, lack of sleep, and a shortage of social interactions. Internet addiction also features the hallmarks of dependence, including salience, mood modification, tolerance, withdrawal, conflict, and relapse.

Salience occurs when being online becomes the most important activity in the individual's life and dominates his or her thinking (preoccupations and cognitive distortions), feelings (cravings), and behavior (deterioration of socialized behavior).

Mood modification refers to the subjective experiences that Internet users report as a consequence of engaging in online activities, and can be seen as a coping strategy, such as the escape appeal of the Internet.

Tolerance is the process whereby increasing amounts of Internet use are required to achieve the former mood-altering effects. Withdrawal symptoms are the unpleasant feeling states and/ or physical effects that occur when Internet usage is discontinued or suddenly reduced, for instance, shakes, moodiness, and irritability.

Conflict means Internet use interferes with the individual's occupational, social, and/or recreational dimensions of life, including conflicts between the Internet users and those around them (interpersonal conflict), conflicts with other activities (job, social life, hobbies, and interests), or conflicts within the individuals themselves (intrapsychic conflict and/or subjective feelings of loss of control), which are concerned with spending too much time engaged in online activities.

Relapse is the tendency for repeated reversions to earlier patterns of Internet use to recur, and for even the most extreme patterns typical of the height of excessive Internet usage to be quickly restored after years of abstinence or control.

A number of studies have explored the risk factors for Internet addiction, including internal factors, namely personality and motivations of addicts, as well as external factors, such as Internet access and Internet activities. The personality traits of Internet addicts appear to involve introversion, neuroticism, and impulsivity, such as loneliness, shyness, avoidance, aggression, hostility, and low self-esteem. The motivations related to dysfunctional coping, socialization, and personal satisfaction seem to serve as risk factors for Internet addiction. Some characteristics of the Internet such as accessibility, affordability, anonymity, and acceptability, appear to make Internet users addicted to it easily, especially those who already have certain preexisting addictions or those who have psychological vulnerabilities rendering them at risk for developing such compulsivity. Prior research has speculated that specific online applications, especially entertainment applications with highly immersive or interactive features, appeared to play a significant role in the development of pathological Internet use. Violent and sexually explicit content on the Internet is another major concern.