3. Introduction

The behavioural addiction brought on by excessive internet use has become a rising source of concern [1] since the last decade. According to clinical studies, individuals with Internet Addiction or Internet Gaming Disorder may have a range of biopsychosocial effects and is classified as an impulse-control disorder owing to its resemblance to pathological gambling and substance addiction [2, 3].

Internet Addiction has been defined by researchers as a person’s inability to resist the urge to use the internet, which has negative effects on their psychological well-being as well as their social, academic, and professional lives [4].

The symptoms can have serious physical and interpersonal repercussions and are linked to mood modification, salience, tolerance, impulsivity, and conflict [5]. In severe circumstances, people may experience severe pain in their bodies or health issues like carpal tunnel syndrome, dry eyes, irregular eating and disrupted sleep [6]. Additionally, Internet Addiction is significantly linked to comorbidities with other psychiatric disorders [7].

Stevens et al (2021) reviewed 53 studies including 17 countries and reported the global prevalence of Internet Addiction was 3.05% [8]. Asian countries had a higher prevalence (5.1%) than European countries (2.7%) [8]. Strikingly, adolescents and young adults had a global Internet Gaming Disorder prevalence rate of 9.9% which matches previous literature that reported historically higher prevalence among adolescent populations compared to adults [8, 9].

Over 80% of adolescent population in the UK, the USA, and Asia have direct access to the internet [10]. Children and adolescents frequently spend more time on media (possibly 7 hours and 22 minutes per day) than at school or sleeping [11]. Developing nations have also shown a sharp rise in teenage internet usage despite having lower internet penetration rates [10].

Concerns regarding the possible harms that overt internet use could do to adolescents and their development have arisen because of this surge, especially the significant impacts by the COVID-19 pandemic [12]. The growing prevalence and neurocognitive consequences of Internet Addiction among adolescents makes this population a vital area of study [13].

Adolescence is a crucial developmental stage during which people go through significant changes in their biology, cognition, and personalities [14]. Adolescents’ emotional-behavioural functioning is hyperactivated, which creates risk of psychopathological vulnerability [15]. In accordance with clinical study results [16], this emotional hyperactivity is supported by a high level of neuronal plasticity. This plasticity enables teenagers to adapt to the numerous physical and emotional changes that occur during puberty as well as develop communication techniques and gain independence [16]. However, the strong neuronal plasticity is also associated with risk-taking and sensation seeking [17] which may lead to Internet Addiction.

Despite the fact that the precise neuronal mechanisms underlying Internet Addiction are still largely unclear, functional magnetic resonance imaging (fMRI) method has been used by scientists as an important framework to examine the neuropathological changes occurring in Internet Addiction, particularly in the form of functional connectivity [18]. fMRI research study has shown that Internet Addiction alters both the functional and structural makeup of the brain.

We hypothesise that Internet Addiction has widespread neurological alteration effects rather than being limited to a few specific brain regions. Further hypothesis holds that according to these alter ations of functional connectivity between the brain regions or certain neural networks, adolescents with Internet Addiction would experience behavioural changes. An investigation of these domains could be useful for creating better procedures and standards as well as minimising the negative effects of overt internet use.

This literature review aims to summarise and analyse the evidence of various imaging studies that have investigated the effects of Internet Addiction on the functional connectivity in adolescents. This will be addressed through two research questions:

(1) How does Internet Addiction affect the functional connectivity in the adolescent brain?
(2) How is adolescent behaviour and development impacted by functional connectivity changes due to internet addiction?