Both the histograms picture and the test results refer to non-normal distribution for the variables of Age (Kolmogorov-Smirnov: p < 0,05. Shapiro-Wilk: p < 0,01), WISC (Kolmogorov-Smirnov: p < 0,01. Shapiro-Wilk: p < 0,01) and BDI (Kolmogorov-Smirnov: p < 0,05. Shapiro-Wilk: p < 0,01). Boxplots revealed the existence of outliers for the variables of WISC (case 21, score 41) and BDI (case 46, score 55). Although it is recommended in statistics to delete outliers, it was decided to maintain them in the present study due to their clinical value. Taking into consideration the above data about non-normal distribution and the existence of outliers, non-parametric tests were applied.
During the exploratory analysis, it was examined whether the answers of the participants were differentiated in regard to the characteristic of sex. For this purpose, the Mann-Whitney test was applied with sex as an independent variable and the scores of Age, WISC and BDI as dependent ones [see Table 1, Additional File 1].
The results showed that for all three variables there were no statistically significant differences between boys and girls in their answers: Age U = 273,00. exact p = 0,67, WISC U = 183,50. exact p = 0,15, BDI U = 214,00. exact p = 0,23. Therefore, the processing included the total of data.
Research of diagnosis
In total 50 children and adolescents with a mean age of 15 years participated in the study. 42,9% of participants were boys and 57,1% girls. The application of Binomial test demonstrated that the deviation in distribution was not statistically significant (exact p = 0,39). The mean WISC score of the participants was 95 points and the mean BDI score was 17,7 [see Table 1, Additional File 1]. In table 2 [Additional File 1], we present in detail the mean scores and standard deviations of each BDI question. The highest mean scores were observed in the questions “Change of sleep” and “Difficulty of concentration”, while the lowest ones in the questions “Loss of interest in sex” and “Suicidal ideas”.
In regard to the total BDI score, we considered a score of 17 as the differentiating point of depressive mood, taking into consideration the proposal of Yannakou et al (2013). In the present research, 23 out of 47 BDI participants had a total score of 17 and above.
Distribution of diagnosis (diagnosis-related groups):
44,9% in the F30-F39 category, [manic episode, bipolar affectional disorder, depressive episode, recurrent depressive disorder, persistent mood disorders(cyclothymia, dysthymia), other mood disorders (ICD-10)] [see distribution of diagnosis, Diagram 1, Additional File 2].
20,4% in the F40-F48 category, [neurotic and somatoform disorders, such as phobic anxiety disorder, anxiety disorders, obsessive–compulsive disorder, adjustment disorders, dissociative disorders]
10,2% in the F50-F59 category, [eating disorders, sleep disorders, sexual dysfunction, substance abuse. Importantly, this category includes anorexia nervosa]
2% in the F60-F69 and F70-F79 categories, [personality disorders and mental retardation respectively].
10,2% in the F80-F89 category, [developmental disorders of speech and language, disorders of scholastic skills and pervasive developmental disorders].
4,1% in the F90-F99 category, [hyperkinetic disorders, conduct disorders, emotional disorders with onset specific to childhood, tic disorders, disorders of social functioning with onset specific to childhood].
6,1% in the Double Diagnosis category
Sleep disorders also scored high in the group through the BDI (22,4%)
Frequency distribution ofBDI questions
In the present unit, chi-square goodness-of-fit test was applied. The goal was to investigate whether the participants choose a score with the same frequency in each BDI question or whether they differentiate [see Table 3, Additional File 1] 1. As Table 2 [Additional File 1] portrays, the participants differentiated as to their answers, except for questions “Reduction of energy, Change of sleep, Difficulty of concentration”, where answers were distributed with more uniformity. In general, participants tended to select the first two scores, which refer to lack or less gravity of symptoms. Selection of increased scores, referring to more grave symptoms was noted in questions “Pessimism, Reduction of energy, Difficulty of concentration”.
In the last question referring to loss of interest in sex, the number of unanswered elements rises to 22,4% and it is the highest compared to the rest of the questions (38 people versus 45 or 46). Thirty adolescents (61,2%) selected the answer “I have not noticed any recent change in my interest in sex”, 3 adolescents (6,1%) were less interested in sex than they used to be, 2 adolescents (4,1%) had almost no interest in sex and 3 adolescents (6,1%) had lost interest in sex completely.
The vast majority of answers sums to the first score selection referring to answer “I have not noticed any recent change in my interest in sex”, which corresponds to score 0. Quite some youth in the group we studied have no sexual intercourse.
Among the BDI questions, only in question 12 (Loss of interest) there was noted a statistically significant difference (early: 18,36, middle: 22,83, late: 31,32, χ2(2) = 6,99, p < 0,05).
In regard to sleep disorders in our sample, in the analytical form, the answers of BDI question 16 (Change of sleep) were distributed as follows:
I sleep as well as usual (0): 11 (22,4%)
I sleep a little more than usual (1a): 9 (18,4%)
I sleep a little less than usual (1b): 10 (20,4%)
I sleep much more than usual (2a): 5 (10,2%)
I sleep much less than usual (2b): 5 (10,2%)
I sleep most hours of the day (3a): 1 (2,0 %)
I wake up 1-2 hours early and can’t go back to sleep (3b): 5 (10,2%)
For the investigation of a potential correlation between the adolescence period with the intelligence level and the BDI score, participants were divided in three categories: early adolescence (10-13 years), middle adolescence (14-17 years) and late adolescence (17-21 years). Fourteen of the participants belonged to the first category, 24 in the second and 12 in the third. See distribution of diagnosis in boys and girls in Diagrams (Pie Charts) 2 and 3, respectively [Additional File 2].
Afterwards, the non-parametric Kruskal-Wallis test was applied with the adolescence stage as independent variable and WISC and BDI scores as dependant variables.
The application of Kruskal-Wallis test showed that the median scores in each subcategory do not differ to a statistically significant degree in regard to the scoring of the participants in the WISC test (early: 20,68, middle: 21,89, late: 29,33, χ2(2) = 2,70, p = 0,26) and in the BDI (early: 23,92, middle: 23,46, late: 25,23, χ2(2) = 0,13, p = 0,94). Among the sub-questions of the BDI, a statistically significant difference was observed only in question 12 (Loss of interest) (early: 18,36, middle: 22,83, late: 31,32, χ2(2) = 6,99, p < 0,05).
In conlusion, the participants did not differentiate as to their WISC and BDI scores in regard to the adolescence stage they were going through (early, middle, late). There is, however, the exception of the sub-question “Loss of interest”, where the highest scores were observed in late adolescence, while the lowest on33es in early adolescence.
Summary presentation o results
Diagnosis distribution: 44,9% in the F30-F39 category, 20,4% in the F40-F48 category, 10,2% in the F50-F59 category, 2% in the F60-F69 and F70-F79 categories, 10,2% in the F80-F89 category, 4,1% in the F90-F99 category, 6,1% in the Double Diagnosis category. No differentiation in regard to sex was observed. We found a similar number of boys and girls, mean WISC score of the participants: 95 points, mean BDI score of the participants:17,7. Higher BDI mean scores were noted in the questions “Changes in sleep” and “Difficulty in concentration”, while lower BDI mean scores were noted in the questions “Loss of interest in sex” and “Suicidal thoughts”. 23 out of 47 BDI participants had a total score of 17 and more. In the questions Pessimism, Reduction of energy and Difficulty in concentration, we observed an increased selection of scores that indicate more grave symptoms. In the question of Loss of interest in sex, , the number of unanswered elements was 22,4%, that is the highest in comparison to the other questions (38 people versus 45 or 46). The vast majority of participants selected the first score choice. No correlations were observed among the variables Age of participants, WISC and BDI. The participants did not differentiate as to their WISC and BDI scores with regard to their adolescence stage (early, middle, late). The only exception was the sub-question of Loss of interest, where the highest scores were noted in late adolescence and the lowest ones in early adolescence.