Brief report
Depression like characteristics of 5HTTLPR polymorphism and temperament in excessive internet users

https://doi.org/10.1016/j.jad.2007.10.020Get rights and content

Abstract

Introduction

Excessive internet use (EIU) has been reported to be comorbid with depression and the manifestation of its symptoms. This study examines the characteristics of excessive internet users that are similar to those of patients with depressive disorders in terms of serotonin transporter gene expression and harm avoidance.

Methods

91 male adolescents with EIU and 75 healthy comparison subjects were recruited. Between group comparisons were made on genetic polymorphisms of the serotonin transport gene and with respect to novelty seeking and harm avoidance (HA) of Cloninger's Temperament Character Inventory.

Results

The homozygous short allelic variant of the serotonin transporter gene (SS-5HTTLPR) is more frequent in the EIU group (χ2 = 4.38, df = 1, p < 0.05). The HA and Beck Depression Inventory (BDI) scores were significantly higher in the EIU group than in the healthy comparison group (t = 7.03, df = 164, p<0.01; t = 2.12, df = 164, p = 0.04). EIU subjects expressing SS-5HTTLPR also showed higher HA (HA1, HA2, HA4, and total HA) and Young's internet addiction scale scores than EIU subjects expressing the other serotonin transporter gene allele variants (t = 2.47, df = 89, p = 0.01; t = 2.33, df = 89, p = 0.02; t = 2.17, df = 89, p = 0.03; t = 2.25, df = 89, p = 0.03; t = 2.93, df = 89, p < 0.01 respectively).

Conclusions

The EIU group had higher SS-5HTTLPR frequencies, harm avoidance, and BDI scores. SS-5HTTLPR expression was closely related to harm avoidance in EIU. The results of this study suggest that EIU subjects may have genetic and personality traits similar to depressed patients.

Introduction

The phenomenon of excessive internet use as a distinct entity within the addictive disorders continues to be the subject of debate (Kraut et al., 1998, Mitchell, 2000, Campbell et al., 2006). However, studies have shown that the addiction-like qualities of EIU may be responsible for behavioral problems including social isolation, depressed mood, and unstable impulsivity (Young, 1998, Reirdan, 1999). These symptoms are similar to those found in depression and anxiety disorders (Kraut et al., 1998, Shapira et al., 2000, Moody, 2001). In an association study between excessive internet use and depression, Kraut et al. (1998) showed that subjects with excessive internet use demonstrated loneliness, decline in communication with household family members and social withdrawal. Major depression is known to be one of the most common comorbid psychiatric disorders in Korean adolescents with EIU (Ha et al., 2006). Ha et al. (2007) also reported that adolescents with excessive internet use had high harm avoidance, low self-directedness, low cooperativeness and high self-transcendence, which are all seen in depression.

The serotonin reuptake transporter gene (5HTT) located on chromosome 17q11.1-q12 has a functional polymorphism in the variable repeat sequence in the promoter region (5HTTLPR) (Ramamoorthy et al., 1993, Lesch et al., 1996). 5HTTLPR may be important in the fine-regulation of serotonergic neurotransmission; the homozygous long allelic variant (L) is associated with higher concentrations of 5HTT messenger RNA and a greater rate of reuptake than variants containing the short allelic variant (S) (Lesch et al., 1996, Greenberg et al., 1999). These findings have led to suggestions that this 5HTTLPR polymorphism (specially, the presence of the S allele of 5HTTLPR) may play a key role in the etiology of depression (Blier and de Montigny, 1999, Wrase et al., 2006) and substance dependence (Lesch, 2005).

The Temperament and Character Inventory (TCI), developed by Cloninger and colleagues, has been widely used in research on psychobiological human behavior (Cloninger, 1987). Among the four dimensions of temperament, novelty seeking and harm avoidance are thought to be correlated with depression (Serretti et al., 2006, Jylha and Isometsa, 2006). Serretti et al. (2006) reported that S allele homozygote of 5HTTLPR was associated with low novelty seeking scores in mood disorder patients. Jylha and Isometsa (2006) demonstrated that harm avoidance is associated with depressive and anxiety symptoms in a normal population. Recently, Ha et al. (2007) also reported the association of harm avoidance and excessive internet use in adolescents with excessive internet use.

Based on these studies, we hypothesized that the EIU group will have characteristics similar to those of patients with depressive disorder in terms of genetic distribution and the harm avoidance dimension of TCI. To the best of our knowledge this is the first genetic polymorphism study of the serotonin and norepinephrine systems in EIU subjects.

Section snippets

Materials and methods

The design of this study was carried out in two phases. Subjects were first screened using self-report questionnaires and the Internet Addiction Scale (IAS)(Young, 1998). Two psychiatrists then conducted the interview with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Health Disorders-IV (SCID) (with emphasis on the pathological gambling criteria) and assess subjects for the presence of other psychiatric disorders (D.H.H and Y.S.L; inter rater reliability (n = 

Results

There was no significant difference with regard to age and education years between the EIU and control groups (Table 1). The mean time of internet use, the mean Young's internet addiction scale score and the mean BDI score of the EIU group were 2.2 ± 1.7 h/day, 68.8 ± 10.5, and 9.0 ± 3.0, respectively. The mean time of internet use, the mean Young's internet addiction scale score, and BDI score of the control group were 0.8 ± 0.39 h/day, 27.00 ± 4.13, and 6.2 ± 2.16, respectively.

The homozygous short

Discussion

In current results, short allele 5HTTLPR homozygote and higher harm avoidance were related with excessive internet use. The BDI scores in excessive internet use group were also higher than that in healthy comparisons.

Serotonergic neurotransmission has been a major focus of pharmacological treatment of mood and anxiety disorders (Blier and de Montigny, 1999). Several in vitro and postmortem studies have explored the role of 5HTTLPR polymorphism and the reuptake of synaptic serotonin (Little et

Role of funding source

Funding for this study was provided by the Korean Ministry of Health and Welfare Grant KMH2004. However, the Korean Ministry of Health and Welfare had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.

Conflict of interest

All authors are agreed not to have any actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations within three (3) years of beginning the work submitted that could inappropriately influence, or be perceived to influence, our work.

Acknowledgements

We thank Dr. Chang Hyun Kim and Sang Wook Kim,who kindly provided the data necessary for our analysis.

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