Functional and structural brain changes in problematic internet use

Problematic internet use has been found to be associated with molecular as well as functional and structural alterations in those brains areas which have been implicated in the development and maintenance of substance-related and addictive disorders (Kuss &

Griffiths, 2012). Liu et al. (2010) in an fMRI study examined the encephalic functional characteristics of problematic internet users and compared these to control groups by applying the regional homogeneity (ReHo) method under resting conditioning. They revealed that problematic internet users showed abnormalities (enhanced synchronization) in regional homogeneity and enhancement of synchronization in encephalic regions such as the cerebellum, brainstem, limbic lobe, frontal lobe and apical lobe. They interpreted these dysfunctions as abnormalities associated with the reward pathway. Regarding this, impairments in this pathway have been associated with the initiation and exaggeration of substance-related and addictive disorders (Edward & Koob, 2010; Robinson & Berridge, 1993; 2001, 2003; Volkow, Fowler, & Wang, 2003).

Zhou et al. (2011) investigated brain gray matter density (GMD) changes in adolescents with problematic internet use using voxel-based morphometry (VBM) analysis on

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resolution T1-weighted structural magnetic resonance images. They found lower GMD in problematic internet users in the left anterior cingulate cortex, left posterior cingulate cortex, left insula and left lingual gyrus compared to their control group. Previously, these brain areas have been associated with processes related to the regulation of emotional behaviour.

Zhou et al. proposed that changes in the GMD reflect changes associated with the functional processes related with these brain areas. This assumption has been validated with evidence that has found problematic internet use was highly associated with behavioural and emotional problems (see subsection 1.6: Risk factors associated with problematic internet use, for an extensive review). Thus, Zhou et al. interpreted their findings as providing support for vulnerability markers associated with structural brain alterations in problematic internet use. Moreover, dysfunctions in these brain areas have been implicated in connection with other addictive behaviours (Goldstein et al., 2007; Naqvi et al., 2007).

Moreover, Lin et al. (2012) researched white matter integrity in a sample of adolescents with problematic internet use. Overall results revealed abnormalities in white matter integrity in some brain areas including: the orbito-frontal white matter, corpus callosum, cingulum, inferior fronto-occipital fasciculus, and corona radiation, internal and external capsules. These have been indicated as playing a role in emotional processing, cognitive control and decision-making processes. This evidence further validates the assumption of there being similarities in the pathogenesis of problematic internet use with that of substance-related and addictive disorders. Research has shown that dysfunctions in these cognitive processes, as well as the structural and functional brain alterations underlying them, can play a role in the development and maintenance of substance-related and addictive disorders (Grant et al., 2006; Romero, Asension, Palau, Sanchez, & Romero, 2010; Volkow et al., 2003). On a molecular level, Hou et al. (2012) and Kim et al. (2011) found reduced dopamine transporters as well as reduced dopaminergic receptor availability in the striatum which are similar outcomes to findings from the field of substance-related and addictive disorders (Di Chiara, 2002; Thomas, Kalivas, & Shaham, 2008; Volkow et al., 2004). It has been suggested that reduced levels of dopamine might be associated with reward deficiency and as such predispose individuals towards the rewarding effects of substance-related and addictive disorders in an attempt to try to optimize an innate deficit of experiencing natural rewards, a state known as anhedonia (Volkow et al., 2013).

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Even though the evidence (subsections 1.9.1 and 1.9.2) described above might suggest there are similarities in the pathogenesis of problematic internet use and substance-related and addictive disorders, which is accordingly to a syndrome model of addiction (Shaffer et al., 2004), there are nevertheless various factors which warrant further research. More specifically, the aforementioned evidence cannot infer causality as the majority of extant studies are cross-sectional. For example, deficits in inhibitory control or functional and structural alterations in brain areas associated with the reward pathway and inhibitory control, can be both vulnerability markers as well as consequence of excessive internet use.

Therefore, a longitudinal design could better elucidate the directionality of the aforementioned relationships and enhance our knowledge of the causes and consequences associated with problematic internet use. In addition, researchers have being reporting on internet use in the aforementioned studies without clearly stating if their work is related to specific potential subtypes such as gaming or social networking etc. (Young, 1999).

Considering the evidence which has shown that there are in fact differences between these (see subsection 1.2), further research is warranted in order to provide a better understanding of the different factors associated with each potential subtype of problematic internet use.

As mentioned above, problematic internet use has been conceptualized as similar to substance-related and addictive disorders due to the commonalities in their symptomatology.

A core similarity between them is that a problematic internet user is characterized by persistence in continuing to use it despite the rise of negative consequences in the user’s life which is similar to addicted individuals continuing to consume substances or gamble even when they know that these actions will have adverse consequences on themselves and others around them. A substantial amount of research in the field of substance-related and addictive disorders has been devoted to trying to identify the underlying mechanisms which mediate this type of behaviour. Thus, in this thesis the aim is to investigate whether similar factors can account for the initiation and maintenance of problematic internet use. Emphasis has been given to the assessment of cognitive processes such as decision-making, attentional bias and inhibitory control as well as physiological functioning as impairments concerning the aforementioned processes have been reliably evidenced as markers of addictive behaviours. These processes involve both higher-order/explicit and automatic/implicit

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cognitions. Explicit cognitions relate to goal-directed processes and depend upon our ability to evaluate the various available options and make decisions which will lead to an optimal outcome. Similarly, this depends upon our capacity to be able to control/inhibit our behaviour accordingly to adopt a goal-directed one. In contrast, implicit cognitions refer to processes which are influencing and guiding behaviour but are outside our awareness (Fazio

& Olson, 2003). With regards to addictive behaviour there is increasing appreciation that implicit cognitions might better elucidate the underlying processes associated with them and as a consequence be very informative for enhance understanding and generating treatments (Wiers & Stacy, 2006). However, both types of cognition have been proven valuable for aiding our understanding of the different processes involved in the various stages of addictive behaviour. In light of this, investigating the applicability of both implicit and explicit cognitive processes in problematic internet use can enhance our understanding of the underlying mechanisms which associate with its initiation and maintenance, and at the same time, help in evaluating its relationship with other types of addictions.

For example, research has revealed that the uncontrollable urge to consume a drug without the consideration of potential the negative outcomes reflects impairments in cognitive and physiological functioning of addictive individuals. More specifically, an addicted individual’s decision-making process is characterized by immediate gratification without assessment of the future consequences of such choices (Bechara & Damasio, 2002;

Bechara, Dolan, & Hindes, 2002; Bechara et al., 2001; Brand, Recknor, Grabenhorst, &

Bechara, 2007; Brevers, Cleeremance, Goudriaan et al., 2012; Goudriaan et al., 2005, 2006).

This pattern of cognitive functioning has been said to partially reflect impairments in the capacity for emotional integration (physiological functioning) into current decision-making processes when future consequences are considered (Bechara & Damasio, 2002; Bechara, Damasio, Damasio, & Lee, 1999; Bechara et al., 2002; Damasio, 1994; Goudriaan et al., 2006). According to this, emotional integration is vital when considering the various outcomes of our choices and as such, can help us guide our decisions towards advantageous outcomes. It has been found that the stimuli related to substances of abuse have the power to “highjack” behaviour and elicit automatic responses amongst addicted population (Brevers, Cleeremans, & Bechara et al., 2011; Cousijn et al., 2013; Dickter & Forestell, 2012; Duka & Townshend, 2004; Field & Cox, 2008; Field, Mogg, Mann, Bennett, &

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Bradley, 2013; Honsi, Mentzoni, Molde, & Pallesen, 2013; Robinson & Berridge, 1993; van Holst, van den Brink, Veltman, & Gourdiaan, 2010). For example, when the stimuli from such substances are encountered these have the power to control behaviour and cognition at the expense of more adaptive behaviours. Additionally, a substantial body of evidence indicates that addicted individuals show impairments in their ability to reflect upon this behaviour and control the initiated automatic responses (Adams et al., 2012; Bechara &

Damasio, 2005; Billieux et al., 2010; Brevers, Cleeremance, Goudriaan et al., 2012; Fleming

& Bartholow, 2014; Fuentes et al., 2006; Goudriaan et al., 2005; Kertzman et al., 2008;

Kreusch et al., 2013; Lopez-Caneda et al. 2014; Lorains et al., 2014; Noel et al., 2005, 2007;

Pike et al., 2013; Rose & Duka, 2008; Verdejo-Garcia et al., 2008, 2012; Weafer & Fillmore 2012; Wiers & Stacy 2006; Wiers et al., 2007).

Overall, it has been argued that interaction of the aforementioned processes underlies vulnerability pertaining to the initiation and maintenance of substance-related and addictive disorders. Considering that problematic internet use has been conceived as a type of behavioural addiction, one would expect the same processes to be associated with its initiation and continuation. However, there is currently limited evidence supporting such a claim. Thus, in my thesis I aim to investigate whether these markers of substance-related and addictive disorders are also evident in problematic internet use. In the following paragraphs I describe the theoretical models related with each vulnerability factor and hence provide a robust account of the underlying mechanisms involved along with a potential theoretical model of problematic internet use.