Participants

A total of 49 children aged 13 to 18 years were included in the cohort. The study group consisted of 22 children who presented at the clinics of Meuhedet Health Services (Northern District), one of the four publicly funded health maintenance organizations in Israel, between September 2016 and September 2017. All were diagnosed with ADHD by a senior pediatric neurologist using teacher and parent questionnaires followed by interviews with the child and at least one parent. The final diagnosis was based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th (1994) or 5th (2013) edition (DSM IV/V) [11, 12]. The control group included 27 otherwise healthy children without ADHD who presented at the Pediatric Neurology and Epilepsy Center of Schneider Children’s Medical Center of Israel, a major tertiary pediatric hospital or at the Meuhedet Health Services (North District, Israel) clinics during the same time period because of a mild/moderate headache or simple viral infection. Inclusion criteria for all study participants were ability to speak and read Hebrew, attendance in a mainstream school, and absence of a severe learning disability or a psychiatric comorbidity (such as anxiety disorder, oppositional disorder, depressive disorder) requiring treatment or psychiatric intervention. None of the children had developmental coordination disorder. One child had Tourette syndrome with variable tics that did not need treatment.

The study was approved by Helsinki Committee of Rabin Medical Center. The parents or guardians of all children provided written informed consent prior to enrolment in the study.

Procedure

Handwriting samples were collected from all participants. The children were given a blank sheet of paper and a blue pen and asked to write a story in Hebrew of 10–12 lines over a 20-min period. The papers were collected and submitted for analysis to a licensed forensic graphologist (B.C.-K.) who was blinded to the background and clinical data of the subjects.

Graphology analysis

The graphologist established a predefined handwriting profile of individuals with ADHD based on graphology theory that handwriting can determine the type of personality and evaluated each sample accordingly. The profile was composed of 15 characteristics: text layout (spread out); margins (none or only one); line direction (never ascending); line, word and, letter spacing (all abnormal); nonconventional letters (many); handwriting slant (never to the right or ascending); deviation of handwriting (yes), letter size (abnormal, 3–4 cm); letter width (only wide or only narrow); continuity or flow connection (absent), shape of writing (never thread-shaped), writing speed (never slow), and strength of graphism (poor). In each sample, 1 point was accorded for every abnormal characteristic identified, yielding a graphology score ranging from 0 to 15. Patients with a score of 9 or more were considered to have ADHD.

Statistical analysis

The graphology scores of the patients with and without ADHD were summarized as mean and standard deviation and compared between the groups, total and stratified by sex. Since scores showed a non-normal distribution, the non-parametric Mann-Whitney U test was used for data analyses. All tests were two-tailed, and the level of significance was set at p < 0.05. Chi-square test was used to compare categorical variables.

The diagnostic accuracy of the graphology evaluation was examined using receiver operating characteristic (ROC) curve analysis, which depicts sensitivity by 100% specificity for every possible cutoff score, with a resulting area under the curve (AUC) ranging from 0.5 (no better than chance) to 1 (perfect diagnostic accuracy). An AUC of 0.8 or higher suggests that an instrument can be considered a useful screening tool [13]. Sensitivity, specificity, positive/negative likelihood ratios (LR), and 95% confidence intervals (CIs) were calculated.