Psychopathology and personality in problematic internet users

Elementi psicopatologici e di personalità associati all’uso problematico di internet

PAOLO ROMA1, FEDERICA RICCI2, GEORGIOS D. KOTZALIDIS3, BENEDETTA GUIDARELLI4,
CORINNA PANCHERI1, CRISTINA MAZZA1, MARIA ELENA CINTI1, FRANCO BURLA1,
STEFANO FERRACUTI1
*E-mail: paolo.roma@uniroma1.it

1Department of Human Neuroscience, Faculty of Medicine and Dentistry, Sapienza University of Rome
2IRCSS San Raffaele of Rome
3NESMOS Department, Faculty of Medicine and Psychology, Sapienza University of Rome
4Private psychologist in Rome, Italy


SUMMARY. Few studies have addressed the issue of psychopathology and personality of individuals with problematic use of internet. In this study we research psychopathological symptoms, personality traits and predictive variables associated with problematic internet use. The study was conducted on a total of 343 students from four Italian Universities using Pathological Internet Use Scale, Big Five Questionnaire, and Symptom Check List 90 Revised. According to this study 52.7% of the sample shows a problematic internet use while only 7.6% don’t suffer from any symptom. More than half of subjects admits to have got into arguments with a significant other over being online, and to have missed social engagements because of online activities. Subjects with problematic internet use scored higher in psychopathological scales. Low levels of Friendliness and Emotional Stability could predict the problematic use of internet. Problematic internet use may be associated with higher psychopathology levels and personality traits.

KEY WORDS. Problematic internet use, Big Five Questionnaire, personality, psychopathology, SCL-90-R.


RIASSUNTO. Pochi studi finora hanno affrontato il problema degli elementi psicopatologici e di personalità associati all’uso problematico di internet. In questo studio vengono analizzati: la psicopatologia, i tratti di personalità e le variabili predittive associati all’uso problematico di internet. Lo studio è stato condotto su un totale di 343 studenti provenienti da quattro università italiane ai quali sono stati somministrati: la Pathological Internet Use Scale, il Big Five Questionnaire e la Symptom Check List 90 Revised. Lo studio ha mostrato che il 52,7% del campione ha un utilizzo problematico di internet mentre solo il 7,6% non ha alcun sintomo. Più della metà dei soggetti ha ammesso di aver discusso con una persona significativa rispetto al fatto di essere spesso online e di aver perso degli impegni sociali a causa delle attività online. Chi ha ammesso di avere problemi di utilizzo di internet ha ottenuto punteggi più alti nelle scale psicopatologiche. Bassi livelli di Cordialità e Stabilità Emotiva potrebbero prevedere un uso problematico di internet. L’uso problematico di internet potrebbe essere associato a livelli più elevati di psicopatologia e a specifici tratti di personalità.

PAROLE CHIAVE. Uso problematico di internet, questionario Big Five, personalità, psicopatologia, SCL-90-R.

INTRODUCTION
Problematic internet use (PIU) is a relatively new entity, for which variants of criteria for impulse control disorders have been proposed, consisting of maladaptive preoccupation with internet use, i.e., irresistible preoccupation or excessive use, conceived as use longer than expected or planned, and clinically significant distress or impairment in social, occupational, or other areas of functioning as a result of internet preoccupation or use1. This ‘technological addiction’2 belongs to the ‘new addictions’, like gambling, shopping addiction, and sex addiction, in which the object is not a chemical substance, but a behavior or a legal, socially acceptable activity3. Nevertheless, among the ‘new addictions’, internet is the most likely to cause problem use due to its easy access, to the time-and-space freedom it allows, and to the sensation of power and control it conveys. In the general population, PIU concerns approximately 1% to 18 % of European users4, and 6% to 11% American users5. A recent Italian study, conducted at High Schools and University Departments in L’Aquila, showed that 23% of the total sample had an internet problematic usage and the 0.7% of total student sample were internet abusers6. Similar results were obtained in another recent Italian study7 where 68% of the student sample spend great amounts of time online and the 9% had a moderate risk to develop the internet abuse.
Adolescents and young adults are the principal users of internet and thus they have greater risk of PIU8,9. Usually men have higher PIU issues than the women10 even if other results are converging toward a homogenization of the frequency11,12. The solicitation to include PIU in the DSM-513,14 did not meet the consent of the DSM-5 Task Force, except for internet gaming disorder, which has been included among Condition for Further Study. However, the DSM-5 cautions not to confuse this proposed entity from excessive internet utilization not involving online game playing, like excessive use of social media, such as Facebook or Tweeter, viewing pornography online, and other types of internet addictive or compulsive use15.
Despite positive effects of internet use on wellbeing were claimed by a longitudinal study16, there are concerns about its increasing pervasiveness and possible destructive consequences which may result in PIU17. Internet addiction has been reported to be comorbid with psychiatric disorders18,19 depression quite frequently10,20-23, but also with attention deficit/hyperactivity disorder24, social phobia25,26, impulse control and addictive disorders27, anxiety disorders28, immature defense mechanism29 and personality disorders30,31. PIU has been related to Cluster A32,33, and particularly with schizotypal personality34, Cluster B with borderline18,31,32, antisocial traits31,32 and narcissistic31 and Cluster C with avoidant traits and obsessive-compulsive18,35.
By now it is not clear to identify whether those psychopathologies are primary or secondary to PIU36,37. PIU may represent a social threat for the future, given its continuous expansion and the simultaneous change in social values and increasing impact on youths; in fact, adolescents with internet addiction have the same psychiatric outlook as adolescents with substance use disorders38, while in high-school students the excessive internet use is related to psychiatric symptoms more than students reporting normal internet use39.
In this research, we are mainly interested in the study of association between non pathological personality traits and PIU. There are few studies about this topic. Problematic users were found to rank high on self-reliance, emotional sensitivity/reactivity, vigilance, and nonconformist characteristics and low on self-disclosure20. Other studies found associations between internet addiction and low self-esteem40, low sensation seeking41, and high shyness42.
Some studies about PIU used the Five Factor Model (FFM) of personality43. It has been observed a lack of relationship between personality and internet use, but lower emotional intelligence in high internet users44. In undergraduate students, extraversion and conscientiousness were inversely associated with internet use, and in a regression model they predicted it more strongly when the model included work drive45. Agreeableness, conscientiousness and emotional stability were found to be negatively correlated with unethical internet use in Malaysian university students46. In Australian undergraduate students, higher scores on impulsiveness items correlated with PIU47. In employees, conscientiousness correlated inversely with PIU48.
As few studies have focused on non-pathological personality, the main objective of this research was to explore the relationships between PIU, the FFM of personality, and psychopathology. The second objective was to evaluate possible predictors of PIU among FFM and general psychopathology. Incidentally, we also evaluated the prevalence of PIU in our sample of Italian internet users and the differences according to the gender.
MATERIALS AND METHODS
Participants
The sample consisted of undergraduate and postgraduate students from four Italian Universities (Milano, Rome, Lecce, Palermo). From October 2015 to February 2016, a total of 343 students (97 from Milan; 101 from Rome; 74 from Lecce; 71 from Palermo) responded to a survey posted at each university website. All university sites posted the questionnaires in the same way. The students learned about the test online by visiting the Campus section or the Facebook profile of the University or were informed by their peers. Students wishing to complete the questionnaire obtained their personal ID access code through contacting the study referent by e-mail.
The mean age of our sample was 22.69 years; SD, 3.57; age range, 18-33 for the whole sample; 190 were female [55.4%] with a mean age of 22.99; SD, 3.59; 153 were male [44.6%] with a mean of 22.31; SD 3.53; age did not differ according to gender [t (341)=1.761; p=.079]).
Years of education did not differ significantly between male (15.11; SD=3.32) and female students (16.01; SD=2.60) [t (341)=1.671; p=.199].
Participants filled out an information sheet on the type of internet usage and on average time spent on the net. Everyone reported using the internet from their smartphone and computer; 58% reported using a tablet as well. The average time spent on the network was for men 2h17min (SD=32 min) and for women 2h25min (SD=48 min) [t (341)=1.769; p=.078].
Problematic internet use
PIU was assessed through the Pathological Internet Use Scale (PIU-S)49. This scale investigates PIU through responses to 13 (true/false) questions evaluating whether internet use was causing academic, work, or interpersonal problems, personal distress, withdrawal symptoms, or mood-alteration. In translating the PIU-S, we considered the peculiarities of psychological scales in the translation process50 and trusted the English-to-Italian translation to a bilingual, English mother tongue psychologist and the back-translation to a bilingual, mainly Italian mother tongue psychiatrist. The translation was approved by the author (personal communication with the first author). Table 1 presents the original items of the PIU scale and the Italian translation. Internal consistency coefficient (α) of the Italian version of PIU Scale was 0.89. The split-half reliability coefficient was 0.81.
Psychopathology
Symptoms were assessed through the Symptom Check-List 90-Revised (SCL-90-R)51. This is a multidimensional self-rating 90-item scale to screen a broad range of psychological problems. Each of the 90 items is rated on a five-point Likert scale ranging from “not at all” to “extremely”, relating to the distress caused by the symptom. The nine primary symptom dimensions are: somatization, obsessive-compulsive, interpersonal sensitivity, depression, anxiety, anger-hostility, phobic anxiety, paranoid ideation, and psychoticism. The checklist has three global indices of distress, the General Severity Index (GSI), a global index measuring overall mental distress, the Positive Symptom Total (PST), and the Positive Symptom Distress Index (PSDI).
Personality according to the FFM
Personality characteristics were assessed through the Big Five Questionnaire (BFQ)52. This questionnaire has been developed to assess the FFM of personality53. The construct validity of the BFQ scales has been demonstrated through their high correlations with similar scales of the NEO-PI for both Italian and American samples54.
The BFQ contains 5 domain scales energy (dynamism and dominance facets), friendliness (cooperativeness and politeness facets), conscientiousness (scrupulousness and perseverance facets), emotional stability (emotion control and impulse control facets), and openness (openness to culture and openness to experiences facets). Each scale contains 24 items, half of which is positively and half negatively phrased as to the scale’s label, to control a possible acquiescent response set. In addition, there is a lie ( L) scale designed to measure a social desirability response set and the tendency to distort meanings of the scores. The L scale contains 12 items that are all positively phrased. For each of the 132 items in the questionnaire, there is a 5-point answer scale that ranges from complete disagreement (1= very false for me) to complete agreement (5= very true for me).
Procedure and statistical analysis
Frequencies and percentage of PIU were computed along with item analyses of the PIU-S. We divided the sample into three clusters of PIU level based on the total score on the PIU-S49, i.e., No Symptoms (NS, a score of 0), Limited Symptoms (LS, PIU scale score 1-3), and Problematic Use (PU, PIU score ≥4). We performed ANOVA with post hoc Scheffé procedure to analyze differences in psychopathological symptoms and personality traits among the above three groups. Bivariate correlations were used to analyze the relationship between personality and psychopathological variables on one side, and internet use on the other. Assuming that areas measured through the BFQ are quite stable personality characteristics, regression analyses were used to identify personality predictors of PIU. PIU was entered as a dependent variable. Independent variables were each of the FFM dimensions. Because of the elevated number of contrasts, we set the level of alpha at .001. All statistics were carried-out through the SPSS-19.
RESULTS
Frequency of PIU
Table 1 shows the frequencies and percentage of ‘pathological’ response to PIU-S items. More than half of participants scored positive on item 1 (57.1%, getting into arguments with a significant other over being online) and 12 (50.7%, missing social occasions due to online activities). More than one third found it hard to stop thinking about online activities after some time they logged out (item 3, 38.2%). Item 8 was the least represented, suggesting that sleep reduction to increase time online could be very typical of PIU.
Mean PIU-S score was 3.39 (SD=2.36; range 0-9) with no differences between men and women (men, mean=3.52, SD=2.33; women, mean=3.28, SD=2.39; t (341)=-.929, p=.354). Table 2 shows the group distribution of PIU (see procedure) in our sample. Only 7.6% of our sample had no symptoms, while a large majority scored high on the questionnaire, i.e., they had significant PIU (52.7%). In our sample, more than 90% of participants admitted that online activities had impacted their daily lives. The frequencies of men and women in the three categories (no, low, and high symptoms) are not significantly different (chi-square test available on request).






Psychopathology at different internet use levels
Table 3 shows the means, standard deviations, results from a series of ANOVAs on SCL-90-R subscales in the three level of internet use, and correlation with PIU scale. Subjects with PIU scored higher in every SCL-90-R subscale. Only this category reached a significant level of symptoms (Positive Symptom Total - PST), according to results on Italian population55. Scheffé comparisons showed that scores on every subscale differed significantly at least in the extreme groups. The correlations between total PIU-S scores and SCL-90-R subscales showed that all psychopathological scales were positively related to PIU.
Big five personality scales at different internet use levels
Table 4 shows means and standard deviations of the BFQ scale score distribution along the three internet use levels and the results of a series of ANOVAs. Problematic users had scored lower with respect to the other two groups on Friendliness and Emotional Stability, and only from the NS on the Energy. Friendliness and emotion stability (Table 4) were inversely correlated to the total PIU score (Energy was also inversely correlated, but this correlation was not so strong). Regression analyses show that low Friendliness and low Emotional Stability could predict PIU (Table 4).






DISCUSSION
This study aimed to correlate PIU, psychopathology and personality in adulthood. We compared three groups composed by individuals with no, limited, and problematic use of internet. The overall prevalence of PIU in our sample of Italian internet users (that was an incidental objectives of this study) was very high. According to the PIU-Scale, more than 50% of our sample reported a PIU, with no gender differences. This rate appears higher than previous European rates, ranging from 1 to 18%4,5,56, and recent Italian results, with a prevalence of 23%6. This could be the effect of recruitment bias and/or of the methodological approaches to the presence of PIU, that in this study was evaluated only through a self-report measure. For this reason, we do not consider it a safe outcome. However, to study the correlations between variables, we believe that this sample of high internet users has been very useful for empirical testing of research hypotheses.
PIU and general psychopathology
We found PIU to be related with likelihood of general psychiatric disorders, as reflected in higher scores of nine SCL-90-R subscales in PIU group. This first outcome is comparable with results of previous studies. Depression in PIU was found in the study of Dong et al.57 and te Wildt58; obsessive-compulsive was found by Dong et al.57 and Jang et al.59; broadband symptoms with anxiety, hostility, sensitivity and psychoticism were found by Dong et al.57. There are also similarities with results obtained by Yen et al.38. These authors used the SCL-90, but employed the Chen Internet Addiction Scale to investigate internet addiction, a scale providing a yes/no PIU cut-off without the stratification we used in this study. They also investigated a younger population than ours (15-21 years vs. 18-33 years). They found higher scores on the hostility, depression, and phobic anxiety SCL-90 scales, but differently from our results, they observed a lower level of anxiety in people scoring high on internet addiction, whereas we found higher anxiety, and also all other symptom scales, which all correlated with scores on the addiction questionnaire. Internet addiction and psychiatric symptoms may increase vulnerability to each other, with psychiatric symptoms leading to onset or persistence of internet addiction, and internet addiction precipitating psychiatric symptoms 38, but the generalized psychopathology we have found in our sample may reflect an increase in psychiatric symptoms severity due to age, and to long-lasting internet addiction persistence.
PIU and personality traits
We found energy, friendliness, and emotional stability to be lower in the heavier internet use group; these dimensions correlated inversely with the PIU-Scale scores. Individuals with low friendliness, (or disagreeableness) are argumentative, uncooperative, and harsh, showing lack of the appropriate social skills, and they are more likely to have negative social interactions44,60,61.
Low emotional stability individuals (neurotic), feel anxious, angry, sad, and cope poorly with stress60. Emotional stability and problematic use of internet were inversely related also in Peters and Malesky61, with the group of problematic internet users scoring lower than the other groups. Online communication offers neurotic individuals (low emotional stability) the opportunity to escape face-to-face interactions that may be more stressful for them. Online communication may also help neurotic individuals to avoid the distress caused by face-to-face interaction61. Internet is becoming a means of coping with stress. Still, neurotic individuals seem to simply be more comfortable with online interaction. Neurotic individuals, as well as introvert individuals, were reported to be able to better express themselves online than during face-to-face interaction62. Neurotic individuals are reported use internet to escape loneliness and to feel as if they are a part of a group63; this may be the pathways to excessive internet use.
Introvert individuals tend to fulfill their unmet social needs online64; this allows them to remain withdrawn from face-to-face social interaction, anonymous, and control the information they release to others45,62. While some previous research has found no relationship between introversion and excessive internet use44, others have found that introverts are more likely to express their true selves online62 and are more likely to be excessive internet users46. The big-five dimension that most closely approaches extraversion is openness; however, in our study openness did not significantly differ among internet use groups and did not correlate with any PIU scale.
Regression analysis showed that disagreeableness and emotional instability in our sample predicted PIU. This result is different from Buckner et al.48, and Mottram and Fleming47, who they find predominantly that low conscientiousness is predictive of misuse of the internet.
However, these two studies use different variables and research designs and are not comparable to the present study.
CONCLUSIONS
The present research appears as a significant contribution to the understanding of PIU. There is few research about PIU, psychopathology, normal personality traits. Our results confirm that PIU individuals have higher psychopathology then non pathological internet users. Among the others characteristics, depression, anxiety and sensitivity are preeminent in PIU subjects. The personality of PIU is constituted of low: energy, friendliness and emotional stability. The last two are significant predictors of PIU.
Our study has several limitations. Given that our online survey was posted through university sites, respondents have self-selected themselves, thus the sample may not be representative of all university students. Furthermore, self-reported measures are bound with higher inaccuracy. Additionally, the multiple questionnaire administration is subjected to the common method bias. Moreover, our design was cross-sectional, preventing inferences about the causal order of relationships from being drawn.
In view of the limitations just exposed, it would be important to replicate this study on a representative population of Italian socio-demographic variables and to extend the study to subjects over 33 years of age or below 15. Moreover, since it is unclear whether the variables of personality is primary, exacerbated or an effect of the PIU, it would be important to be able to carry out a longitudinal study on a sample of initially non-pathological subjects. In addition, the correlations and affinities between PIU profiles and subjects with other types of dependencies should be examined.

Conflict of interests: the authors have no conflict of interests to declare.
references
 1. Tonioni F. Definire la dipendenza da internet. Riv Psichiatr 2013; 48: 97-100.
 2. Griffiths MD. Technological addictions. Clinical Psychology Forum 1995; 76: 14-9.
 3. Young KS. Internet addiction: the emergence of a new clinical disorder. CyberPsychology Behav 1996; 1: 237-44.
 4. Laconi S, Vigouroux M, Lafuente C, Chabrol H. Problematic internet use, psychopathology, personality, defense and coping. Comput Human Behav 2017; 73: 47-54.
 5. Weinstein A, Lejoyeux M. Internet addiction or excessive internet use. Am J Drug Alcohol Abuse 2010; 36: 277-83.
 6. Bianchini V, Cecilia MR, Roncone R, Cofini V. Prevalence and factors associated with problematic internet use: an Italian survey among L’Aquila students. Riv Psichiatr 2017; 52: 90-3.
 7. Iannitelli A, Parnanzone A, Quartini A, et al. Internet use among Italian students: usefulness of Internet Addiction Test. J Psychopathol 2018; 24: 10-5.
 8. Kuss DJ, van Rooij AJ, Shorter GW, Griffiths MD, van de Mheen D. Internet addiction in adolescents: prevalence and risk factors. Comput Human Behav 2013; 29: 1987-96.
 9. Ko CH, Yen JY, Yen CF, Chen CS, Chen CC. The association between Internet addiction and psychiatric disorder: a review of the literature. Eur Psychiatry 2012; 27: 1-8.
10. Carli V, Durkee T, Wasserman D, et al. The association between pathological internet use and comorbid psychopathology: a systematic review. Psychopathology 2013; 46: 1-13.
11. Kaye S, Farrell M. Disorders associated with excessive use of Internet, computers, smartphones and similar electronic devices. In: Proceedings from the First Act of the World Health Organization Congress: Public health implications of behavioral addictions associated with excessive use of Internet, computers, smart phones and similar electronic devices. Geneva, Switzerland: WHO Document Production Services, 2014.
12. Kuss DJ, Griffiths MD, Binder JF. Internet addiction in students: prevalence and risk factors. Comput Human Behav 2013; 29: 959-66.
13. Shapira NA, Lessig MC, Goldsmith TD, et al. Problematic internet use: proposed classification and diagnostic criteria. Depress Anxiety 2003; 17: 207-16.
14. Block JJ. Issues for DSM-V: internet addiction. Am J Psychiatry 2008; 165: 306-7.
15. APA. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington VA: APA Press, 2013.
16. Kraut R, Kiesler S, Boneva B, Cummings J, Helgeson V, Crawford A. Internet paradox revisited. J Soc Issues 2002; 58: 49-74.
17. Young KS. Caught in the net. New York, NY: John Wiley & Sons, 1998.
18. Bernardi S, Pallanti S. Internet addiction: a descriptive clinical study focusing on comorbidities and dissociative symptoms. Compr Psychiatry 2009; 50: 510-6.
19. Floros G, Siomos K, Stogiannidou A, Giouzepas I, Garyfallos G. Comorbidity of psychiatric disorders with Internet addiction in a clinical sample: the effect of personality, defense style and psychopathology. Addict Behav 2014; 39: 1839-45.
20. Young KS, Rodgers RC. Internet addiction: personality traits associated with its development. Paper presented at the 69th annual meeting of the Eastern Psychological Association. 1998.
21. Ko C-H, Yen J-Y, Chen C-S, Chen C-C, Yen C-F. Psychiatric comorbidity of internet addiction in college students: an interview study. CNS Spectr 2008; 13: 147-53.
22. Kraut R, Patterson M, Lundmark 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.
23. Caplan SE. Preference for online social interaction. Communic Res 2003; 30: 625-48.
24. Yoo HJ, Cho SC, Ha J, et al. Attention deficit hyperactivity symptoms and internet addiction. Psychiatry Clin Neurosci 2004; 58: 487-94.
25. Yen J-Y, Ko C-H, Yen C-F, Wu H-Y, Yang M-J. The comorbid psychiatric symptoms of Internet addiction: attention deficit and hyperactivity disorder (ADHD), depression, social phobia, and hostility. J Adolesc Health 2007; 41: 93-8.
26. Rusconi AC, Valeriani G, Carlone C, et al. Internet addiction disorder e social network: analisi statistica di correlazione e studio dell’associazione con l’ansia da interazione sociale. Riv Psichiatr 2012; 47: 498-507.
27. Shapira NA, Goldsmith TD, Keck PE, Khosla UM, McElroy SL. Psychiatric features of individuals with problematic internet use. J Affect Disord 2000; 57: 267-72.
28. Ho RC, Zhang MW, Tsang TY, et al. The association between internet addiction and psychiatric co-morbidity: a meta-analysis. BMC Psychiatry 2014; 14: 183.
29. Bagheri M, Azadfallah P, Fathi Ashtiany A. The comparison of defense and attachment styles in addicted/non-addicted women. J Psychol 2013; 17: 220-36.
30. Morey LC, Hopwood CJ. Stability and change in personality disorders. Annu Rev Clin Psychol 2013; 9: 499-528.
31. 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.
32. Laconi S, Andréoletti A, Chauchard E, Rodgers RF, Chabrol H. Utilisation problématique d’Internet, temps passé en ligne et traits de personnalité. Encephale 2016; 42: 214-8.
33. Sepehrian F, Lotf JJ. The rate of prevalence in the internet addiction and its relationship with anxiety and students’ field of study. Aust J Basic Appl Sci 2011; 5: 1202-6.
34. Truzoli R, Osborne LA, Romano M, Reed P. The relationship between schizotypal personality and internet addiction in university students. Comput Human Behav 2016; 63: 19-24.
35. Yeon B. A study of the relationship between internet addiction tendency and personality disorders. Eur Neuropsychopharmacol 2009; 19: S673-4.
36. Davis RA. A cognitive-behavioral model of pathological Internet use. Comput Human Behav 2001; 17: 187-95.
37. Kuss DJ, Griffiths MD, Karila L, Billieux J. Internet addiction: a systematic review of epidemiological research for the last decade. Curr Pharm Des 2014; 20: 4026-52.
38. Yen J-Y, Ko C-H, Yen C-F, Chen S-H, Chung W-L, Chen C-C. Psychiatric symptoms in adolescents with Internet addiction: comparison with substance use. Psychiatry Clin Neurosci 2008; 62: 9-16.
39. Yang C-K, Choe B-M, Baity M, Lee J-H, Cho J-S. SCL-90-R and 16PF profiles of senior high school students with excessive internet use. Can J Psychiatry 2005; 50: 407-14.
40. Armstrong L, Phillips J, Saling L. Potential determinants of heavier internet usage. Int J Hum Comput Stud 2000; 53: 537-50.
41. Lavin M, Marvin K, McLarney A, Nola V, Scott L. Sensation seeking and collegiate vulnerability to internet dependence. Cyberpsychol Behav 1999; 2: 425-30.
42. Chak K, Leung L. Shyness and locus of control as predictors of internet addiction and internet use. CyberPsychology Behav 2004; 7: 559-70.
43. McCrae RR, Costa PT. The five-factor theory of personality. In: Handbook of personality: theory and research. 3rd ed. New York, NY: Guilford Press, 2010.
44. Engelberg E, Sjöberg L. Internet use, social skills, and adjustment. CyberPsychology Behav 2004; 7: 41-7.
45. Landers RN, Lounsbury JW. An investigation of Big Five and narrow personality traits in relation to Internet usage. Comput Human Behav 2006; 22: 283-93.
46. Karim NSA, Zamzuri NHA, Nor YM. Exploring the relationship between Internet ethics in university students and the big five model of personality. Comput Educ 2009; 53: 86-93.
47. Mottram AJ, Fleming MJ. Extraversion, impulsivity, and online group membership as predictors of problematic internet use. Cyberpsychol Behav 2009; 12: 319-21.
48. Buckner JE, Castille CM, Sheets TL. The Five Factor Model of personality and employees’ excessive use of technology. Comput Human Behav 2012; 28: 1947-53.
49. Morahan-Martin J, Schumacher P. Incidence and correlates of pathological Internet use among college students. Comput Human Behav 2000; 16: 13-29.
50. Simonsen E, Mortensen EL. Difficulties in translation of personality scales. J Pers Disord 2011; 9: 290-6.
51. Derogatis L. SCL-90-R, administration, scoring, and procedures manual for the Revised version. Baltimore, Maryland: Johns Hopkins University, 1977.
52. Caprara GV, Barbaranelli C, Borgogni L. BFQ: Big Five Questionnaire. Manual. Firenze: Organizzazioni Speciali, 1993.
53. Caprara GV, Barbaranelli C, Borgogni L, Perugini M. The “big five questionnaire”: a new questionnaire to assess the five factor model. Pers Individ Dif 1993; 15: 281-8.
54. Barbaranelli C, Caprara GV, Maslach C. Individuation and the Five Factor Model of Personality Traits1. Eur J Psychol Assess 1997; 13: 75-84.
55. Prunas A, Sarno I, Preti E, Madeddu F, Perugini M. Psychometric properties of the Italian version of the SCL-90-R: a study on a large community sample. Eur Psychiatry 2012; 27: 591-7.
56. Achab S, Meuli V, Deleuze J, et al. Challenges and trends of identification and treatment of disorders associated with problematic use of Internet. In: Proceedings from the 1rst Act of the World Health Organization Congress: Public health implications of behavioral addictions associated with excessive use of Internet, computers, smart phones and similar electronic devices. Geneva, Switzerland: WHO Document Production Services, 2014.
57. Dong G, Lu Q, Zhou H, Zhao X. Precursor or sequela: pathological disorders in people with internet addiction disorder. PLoS One 2011; 6: e14703.
58. te Wildt B, Putzig I, Drews M, et al. Pathological Internet use and psychiatric disorders: a cross-sectional study on psychiatric phenomenology and clinical relevance of Internet dependency. Eur J Psychiatry 2010; 24: 136-45.
59. Jang KS, Hwang SY, Choi JY. Internet addiction and psychiatric symptoms among Korean adolescents. J Sch Health 2008; 78: 165-71.
60. John O, Naumann L, Soto C. Paradigm shift to the integrative Big Five trait taxonomy: history, measurement, and conceptual issues. In: Handbook of personality: theory and research. 3rd ed. New York, NY: Guilford Press, 2010.
61. Peters CS, Malesky LA. Problematic usage among highly-engaged players of massively multiplayer online role playing games. Cyberpsychol Behav 2008; 11: 481-4.
62. Amichai-Hamburger Y, Wainapel G, Fox S. “On the Internet no one knows i’m an introvert”: extroversion, neuroticism, and internet interaction. CyberPsychology Behav 2002; 5: 125-8.
63. Amiel T, Sargent SL. Individual differences in Internet usage motives. Comput Human Behav 2004; 20: 711-26.
64. Bargh JA, McKenna KYA, Fitzsimons GM. Can you see the real me? Activation and expression of the “True Self” on the Internet. J Soc Issues 2002; 58: 33-48.