Background: Adolescence can be defined as the period between puberty and adulthood, usually between the ages of 11 and 18 years. Events during this period have a great influence on a person's development and can determine their attitudes and behavior in later life .
The latest research has shown that adolescence can be divided into several stages; early, middle and late. Later on we can consider the post-adolescent phase .
One of the most important functions of adolescence is to develop one’s own perceptions of sexuality, without conflict with oneself and always acting within acceptable moral standards. The easing of parental authority helps to guide the individual through new and independent relationships, reducing dependence on peer groups thus helping to find one's own identity.  Teenagers are often in conflict with authority and the cultural and moral norms of society, so certain developmental effects can trigger a series of defense mechanisms .
For all age groups, from school age to adulthood, the most dominating and uncontrollable emotion is sorrow, which can lead to depression, discouragement and loneliness. These emotions are central to most experiences of depression. These symptoms usually increase with age for females who generally demonstrate a higher degree than males.
During the developmental stages of adolescence there is an increased danger of crises, often accompanied by mood changes, periods of anxiety and depressive behavior which adolescents attempt to fight through withdrawal, avoidance of overly emphasized social contact, aggressive reactions and addictive behavior ,  . Adolescents are exceptionally vulnerable during this period and because of their receptive age can become drawn to the Internet as a release. This can, in time, lead to a type of addiction.
Adolescents are especially attracted to new and technological methods of communication which offer interaction with others and at the same time give them anonymity and an impression of belonging to a community as well as social acceptability. The Internet is a global network which connects millions of people throughout the world, enabling users to exchange information and, importantly, this information is available at any time and any place .
In a very short time the Internet has become the most popular and sophisticated medium for influencing the needs of children and young persons . Access to information is unlimited and it can be a source of amusement as well as a generator of new interests . However the Internet can also represent new and unknown threats. Simple and uncontrolled information access and the anonymity that goes with it can endanger the moral development of the young. The Internet can generate negative attitudes, aggressive feelings and insensitivity to unethical behavior due to the fact that there is no direct contact between individuals.
Factors which can lead to addictive attitudes towards the Internet are depression, loneliness, intimacy, simplicity, availability of approach, anonymity, high level of curiosity paired with strong pressures from ones surroundings. Addiction is often the result of social crises, lack of self-confidence, a need to conform, boredom and the availability of interesting and amusing pastimes . The concept of addictions to particular behaviors or substances has been known for centuries, as have the psychological effects these have. Regardless of extensive knowledge about such tendencies, they do not appear to diminish; on the contrary, these traits seem to be increasingly attractive to some and often become compulsive .
Persons addicted to Internet use have been noticed to have three to five psychiatric disturbances. The most common of these are social phobias, ADD/ADHD, insomnia, behavioral disorders, anxiety, and compulsive attitudes to gambling and other social pastimes . Anxiety issues often affect problem children and adolescents and during this period there is a distinct tendency towards symptoms of depression.
Recent research by Nalwa & Anand points to the fact that the Internet gives students numerous advantages for learning due to the wide access to literature, e-learning, courses etc. However, frequent access to the many unimportant web sites such as those for chat, games etc. can easily cause addiction which could have negative results on their health and standards of learning. Children often abandon traditional pastimes and replace them with time spent surfing the Internet. This can lead to late bed time with the subsequent loss of peaceful sleep. Often life is considered boring without the Internet which can lead to a strong feeling of loneliness .
The purpose of this paper is to observe the psycho social effects of Internet addiction during adolescence. Since the early and middle stages of adolescence are crucial for emotional development, the research dealt with them in particular. Adolescents need time to solve identity crises, affirm their attitudes, and establish social links and professional aims.
Emotional regulators represent an important mechanism through which the child’s own characteristics, as well as those of its surroundings, influence the child’s ability to adapt. It is during this period of adjustment that adolescents are open to the various addictive temptations that the Internet presents.
J.J. Gross defines emotional regulation as the process through which individuals influence which emotions they have, when they have them, and how they experience and express them . In general we can conclude that emotional control helps a person to coordinate expressive feelings with those of the environment (the regulation behavior) and also to protect themselves from uncomfortable feelings. These feelings do not restrain, detract or inhibit normal functioning (the regulation of emotional experience) .
Adolescents tend to be more involved with risky behavior and can indulge in addictive practices in order to more easily cope with anxiety, frustration and failure. Objective: Due to the lack of scientific proof it is difficult to ascertain in which stages do adolescents use the Internet and to what purposes. It is also hard to establish how does the virtual model of life preferred by the Internet addicts influence psycho social functioning and the quality of life.
Since Internet addicts spend most of their time surfing in front of the computer the goal was to establish for which purposes do they most often use the Internet. The goal was also to note whether there are differences between the Croatian, Polish and Finnish adolescents with regards to the purpose of Internet use as well as any possible differences with respect to gender.
H1- There is an influence, a correlation between the purpose of Internet use and the age, and the interaction of the two, on the level of addiction to the Internet. Methods: Participants are defined as students who attend regular school, age 11- 18 years old. The schools that participated in this research are Poljisani Split Viska 12 and „ Blatine-Skrape“ Krzice 2 Split elementary school as well as First Grammar school Teslina 10 21000 Split and Third Grammar school Matice Hrvatske 11 21000 Split.
From Finland the following schools were chosen: Raunistulan koulu, Teräsrautelan koulu / Suikkilan yksikkö, Talinkorventie 16, 20320 Turkish, Finland, Turun suomalaisen yhteiskoulun lukio, Kauppiaskatu 17, FINE-20100 Turkish.
From Poland the following schools participated: Szkoła Podstawowa them. Powstancow Wielkopolskich to the ul. More painfully 2 88-170 Pakość ; Gimnazjum them. Ewerysta Estkowskiego to the ul. Szkolna 44 88-170 Pakość.
Research was carried out with permissions of the ministries in charge of education in Croatia, Poland and Finland, ethical commissions of the schools and with consent of the participants themselves. The schools were issued an invitation to participate with assurances of the complete respect of the privacy of individual students with the informed consent of the students and their parents or guardians. The questionnaire was developed in Google documents format and sent to schools in an electronic form along with instructions and contact information of the researchers. The title page instructed the participants to fill the questionnaires out fully and truthfully. They were informed that participation is anonymous and voluntary, that the data will be used for research purposes only and general and particular importance of the research was pointed out to them. Furthermore, they were notified as to the type and duration of the procedures used and they were informed of the confidentiality of the data gathered and the protection of privacy of the participants. The participants were free to refuse participation or to quit at any time without explanation. Having been notified of all the particulars, they proceeded to fill out the questionnaires.
Method of research
Survey consists of three parts. A standardized procedure of double translation was applied to each part for each country/language.
Demographic parameters used in the research include:
• Gender (1-female ; 2-male)
• Country of residence
• Purpose of Internet use
Participants were asked to appraise whether they use the Internet more often for amusement or educational purposes.
Internet addiction questionnaire
Internet addiction will be assessed using Young’s (1996) IAT (Internet Addiction Test), also known as YIAS (Young’s Internet Addiction Scale). IAT contains twenty questions based on the criteria for pathological gambling. These questions reflect typical addictive behavior. Widiyanto and McMurran report that the scale reflects six dimensions of Internet addiction: salient preoccupation, overuse of the Internet, neglecting work responsibilities, expectation, lack of self-control and neglecting social life. The authors have found that the factors of saliency and overuse are in connection with a more intensive use while neglecting work is only correlated with age and negatively. The conclusion drawn by the authors is that IAT “does measure some of the key aspects of Internet addiction”. .
Level of addiction was graded on a scale, ranging from 20 to 100.
20-49 – Normal
50-79 – Moderate addiction
80-100 – Serious addiction
Each question can score up to 5 points (1 very rarely, 2 rarely, 3 often, 4 very often, 5 always). The scale demonstrates excellent internal consistency with the alpha coefficient of 0.93 in the current studies. Results: 1078 adolescents from Croatia, Poland and Finland participated in the research. The representative sample of n = 1078 comprised of roughly an equal number of participants of both genders: 534 males and 525 females (for 19 of them the gender was unknown). The age varied between 11 and 18, the average age being 14.9 with the average discrepancy of 1.92 years which is a small dispersion (with the variance coefficient of only 13%). Participants were predominantly fifteen year olds so both the median and mode values are 15 years. The structure of the participants sample is shown in Graph 1 with regard to their gender, age, country and the purpose of Internet use.
Graph 1: Structure of polled adolescents with regard to gender, age, orgin and purpose of internet use ( in percentages)
The predominant purpose of Internet use with the 1078 participants is entertainment (84%) with school/work far behind at 16%. Using the chi-square test a correlation was established between the purpose of Internet use and gender and the purpose of Internet use and nationality (country of residence) as can be observed in the following contingency tables (Table 1 and Table 2) used in these tests.
Table 1: Number of interviewed adolescents according to gender and purpose Internet use( n=1078)
The values of chi-square test computed using Table 1 (χ2 = 11,285; df = 1; N = 1042; p = 0.001) point to the conclusion that there is a statistically significant link (p = 0.001) between gender and the purpose of Internet use. What is this link? Female participants use the Internet for school or work related purposes (20%) much more than their male counterparts (12%).
However, if the analyses of this correlation between gender and the purpose of Internet use are carried out separately for each country the results are different:
Table 2: Correlation between gander and purpose of Internet use for each country
This statistically significant link is present with Croatian participants (χ2 = 26,811; df = 1; N = 476; p < 0,001) and it is not present with the Finnish and Polish ones (p > 0,05). Therefore, the Croatian participants have importantly contributed to the conclusion that there is a statistically significant correlation between gender and the purpose of Internet use (in all three countries).
Table 3: Number of interviwed adolescents according to country and purpose Internet use (N=534)
The values of chi-square test computed using Table 3 (χ2= 27,274; df = 2; N = 1058; p < 0,001) point to the conclusion that there is a statistically highly significant correlation between the country and the purpose of Internet use (p < 0,001). For example, the use of Internet for school/work is less in Croatia (16%) than in Poland (24%) with Finland in the last place at only 8%.
There is a statistically significant correlation (χ2 = 19,742; df = 6; N = 919; p = 0,003) between age and the level of Internet addiction. Using the contingency table (Table 3) it is possible to calculate that the percentage of moderate and serious addicts grows simultaneously with the participants’ age:
youngest (11-12) – 6%
slightly older (13-14) – 12%
older (15-16) – 19%
the oldest (17-18) – drops down to 13%
The results show a correlation between age and Internet addiction (χ2= 13,512; df = 3; N = 919; p = 0,004). This correlation can be further broken down by gender, country and the purpose of Internet use. According to gender the adolescents can be categorized as male or female and we can calculate a separate chi-square test for each of these sub-sections in order to ascertain the correlation between the age of adolescents and Internet addiction. This result will show us whether it is the male or the female demographic which contributes to the correlation between age and Internet addiction. The same can be done with the remaining two independent variables – country and the purpose of Internet use. For reasons of exactitude of tests the Internet addiction is expressed on only two levels: normal addiction and moderate and serious addiction.
Table 4: Correlation between age and Internet addiction
So, the males (p = 0,001) and those adolescents who have used the Internet mostly for entertainment purposes (p = 0,038) have mostly contributed to the correlation between the age of adolescents and Internet addiction.
Using correlation analysis, the age was considered as being a continuous independent variable and the Internet addiction as dependent ordinal variable. Non-parametric method was used to calculate the Spearman’s coefficient of correlation of 0,08 for N = 1033 and with p = 0,011. It can be concluded that the correlation between the age of adolescents and Internet addiction is weak, positive and statistically significant.
Two-factor variance analysis was carried out using the following variables:
Dependent quantitative variable = Internet addiction (expressed in points).
This variable was formed as a sum of answers to the twenty questions on Internet use.
First independent categorical variable = purpose of Internet use (factor 1) with two modalities: school/work and entertainment.
Second independent categorical variable = age group (factor 2) with four modalities: 11-12, 13-14, 15-16, 17-18.
This model of two-factor variance analysis is meant to provide answers to the following three questions:
• Is there a statistically significant influence of the purpose of Internet use on the level of Internet addiction (disregarding the age of participants)?
• Is there a statistically significant influence of the age of participants on the level of Internet addiction (disregarding the purpose of Internet use)?
• Is there a statistically significant interaction between the purpose of Internet use and the age of the participants regarding the level of Internet addiction?
In describing the analysis data obtained through the described model, the Levene test of variance equality has to be mentioned first, as it has established that variances are not homogenous (p < 0,001) for the analyzed sample of participants. The p values obtained in the ANOVA table enable us to answer the three questions:
• There is no statistically significant influence of the purpose of Internet use on the level of Internet addiction (disregarding the age of participants), as p = 0,215, that is p > 0,05.
• There is a statistically important influence of the age of participants on the level of Internet addiction (disregarding the purpose of Internet use), as p < 0,001.
• There is a statistically significant interaction between the purpose of Internet use and age regarding the level of Internet addiction (p = 0,001).
Comparing the eight mean values between themselves we are able to conclude where this level of Internet addiction is at its lowest and where at its highest:
11-12 y.o. school/work 32,5
13-14 y.o. school/work 34,8
15-16 y.o. school/work 46,5
17-18 y.o. school/work 38,2
The lowest level of Internet addiction is noted with the youngest who use the Internet for school (32,5). The adolescents between the ages of 15 and 16 who also use the Internet for school have the highest.
Single factor variance analysis (F test) was used to compare the average values of Internet addiction in adolescents of different ages. These average values (points calculated on the basis of the answers to the twenty questions in the questionnaire) according to age groups are:
11-12 y.o. – 32,4
13-14 y.o. – 37,6
15-16 y.o. – 40,6
17-18 y.o. – 36,4
The average score overall was 37,8. There is a statistically significant difference between the four averages (F = 14,461 with df = 3 and N = 919), as p < 0,001. Graphically, these are represented as follows:
Graph 2: compare the average values of Internet addiction in adolescents of diferent ages
1078 adolescents aged 11 – 18 from Croatia, Poland and Finland participated in the research.
The goal of this research was to investigate the existence of differences between the adolescents in Croatia, Poland and Finland with regard to the purpose of Internet use and also to establish whether there are differences between the genders regarding the purpose of Internet use.
The basic purpose of Internet use among the 1078 participants is predominantly entertainment (84%), with only 16% using the Internet for school/work. Female participants use the Internet for school/work significantly more (20%) than their male counterparts (12%).
Croatian participants (16%) use the Internet for school much less than the Polish ones (24%), while the Finnish participants use it the least (just 8%).
Lenhart & Madden got similar results in their research; male adolescents in America use functional and entertainment activities on the Internet much more than the girls who use it for educational and social activities to a much higher degree . Furthermore, similar data was also obtained by Lin & Tsai. They concluded that Taiwanese boys use the Internet to elevate their mood levels, while Taiwanese girls possess a more practical view of the Internet .
Programs and activities on the Internet offer the younger generations new dimensions of social activities, so the use of Internet can expand and reinforce the connection with friends and colleagues 
Tsai and Lin noticed that some adolescents were so preoccupied with activities on the Internet that they were displaying signs of addiction .
In accordance with the correlations of risky forms of behavior and the developmental stages of adolescence, the following hypothesis was accepted: different stages of adolescence show a different percentage of Internet addicts. This means that there is a correlation between the age of adolescents and Internet addiction and it is weak, positive and statistically significant (χ2= 13,512; df = 3; N = 919; p = 0,004).
The percentage of moderate and serious addicts grows with age:
- Youngest (11-12 y.o.) – 6%
- Slightly older (13-14) – 12%
- Older (15-16) – 19%
- Oldest (17-18) – drops down to 13%
The greatest contributors to this correlation are males (p = 0,001) and those adolescents who use the Internet predominately for entertainment (p = 0,038). Adolescents aged 15 – 16 demonstrate the highest degree of addiction, possibly because at this age they achieve a greater level of independence. Their free time and social activities are less controlled by their parents.
Online communication has a strong influence on the developmental stages of adolescence. Adolescents share their experience through new forms of communication; they seek their own position within a group and report their friends as being a great source of social support, even greater than their parents .
A two-factor variance analysis was carried out, utilizing the following variables:
Dependent quantitative variable “Internet addiction” and factor 1, “the purpose of Internet use” with two modalities: school/work and entertainment. The second, independent categorical variable, “age group” had four modalities: 11-12, 13-14, 15-16 and 17-18.
Regarding the analyzed sample of participants:
There is no statistically significant influence of the purpose of Internet use on the level of Internet addiction while there is a statistically significant influence of age of participants on the level of Internet addiction.
There is a statistically significant interaction between the purpose of Internet use and age with regard to the level of Internet addiction (p = 0,001).
Comparing the eight mean values between themselves we established that the lowest level of addiction occurs with the youngest group (11-12 y.o.) who use the Internet for school (32,5). They are also the ones who use the Internet for entertainment the least (32,8). The highest level of Internet addiction occurs with the 15-16 y.o. adolescents. Their purpose of use of the Internet for school is the highest (46,5) of the age groups, as is their use for the purposes of entertainment (39,3). Those aged 13-14 use the Internet more for entertainment (38,2) and less for school (34,2). The 17-18 y.o. group uses Internet at the percentage of 38,2 for school/work and 35,9 for entertainment.
Single factor variance analysis (F test) was used to compare average values of Internet addiction in adolescents of different ages. These averages were calculated on the basis of answers given to the twenty questions in the questionnaire and are:
11 – 12 y.o. – 32,4
13 – 14 y.o. – 37,6
15 – 16 y.o. – 40,6
17 – 18 z.o. – 36,4
The average overall score was 37,8 and there is a statistically significant difference between the four averages (F = 14,461 with df = 3 and N = 919), as p < 0,001. Conclusions: The basic purpose of Internet use among the 1078 participants is entertainment (84%), the secondary school/work (16%). 20% of female adolescents use the internet for school/work, which is significantly more than the males (12%).
Croatian participants (16%) use the Internet for school/work significantly less than the Polish ones (24%) and the Finnish participants use it for school/work the least (only 8%).
Percentage of moderate and serious Internet addicts grows with age. Most addicts are to be found in the middle stage of adolescence, in the 15 – 16 age group.
Furthermore, the purpose of Internet use has no effect on the level of Internet addiction whereas the age is a significant predictor of the level of Internet addiction as is the interaction between the purpose of Internet use and age which also influences the level of Internet addiction.
After comparing the eight mean values between themselves we learned that the lowest level of Internet addiction is found among the youngest group (11-12) that uses the Internet for school (32,5). They also have the lowest rate of Internet use for entertainment (32,8). The highest level of Internet addiction is to be found in the 15 – 16 group. This group has the highest rate of Internet use for school (46,5), but also for entertainment (39,3). 13 – 14 y.o. adolescents use Internet for school at the percentage of 38,2 and for entertainment at 34,2. The numbers for 17 – 18 y.o. group are 38,2 for school/work and 35,9 for entertainment.