The contribution of biological and social factors to the manifestation of learning disorders

Introduction: Learning disorders are among the most common developmental disorders. According to literature, developmental, biological, genetic, social and psychological factors are correlated with development of learning disorders. The strongest evidence to date supports the role of deficits in phonological awareness (i.e. the ability to reflect on the sound structure of spoken words) as the basic component of reading disability.

As far as genetic factors are concerned, current estimates indicate that the risk for a son to develop dyslexia if he has a dyslexic parent is 35-40% and for a daughter 20%, regardless of which parent is affected. It is important, however, not to overlook the critical role of the environment in shaping a child's reading development.

The aim of the present study was to investigate the contribution of biological and social/environmental factors to the manifestation of learning disorders.

Method: The clinical sample comprised of 130 children and adolescents aged 6-18 years who presented to our Unit the period of time 1998-2001 for an assessment due to low educational achievement (76.90% of them were boys and 23.10% of them girls). They were diagnosed with Specific Developmental Disorder of Academic Skills according to the ICD-10 Classification of Mental Disturbances and Behavioural Disorders by the World Health Organization. In 20,7% of these cases a concomitant diagnosis of Specific Language Impairment was made. The control group consisted of 168 children and adolescents of the same age range from schools in our vicinity with excellent scholastic achievement. The following parameters were recorded: gender, age, history of pregnancy and delivery, breastfeeding and medical record of organic diseases. A distinction was made between acute organic diseases, such as infections of the upper respiratory system, otitis media, etc., and chronic organic diseases, such as juvenile diabetes or asthma. In addition, age, occupation and academic achievement of both parents were recorded. The relationship between the aforementioned parameters and the manifestation of learning difficulties was then examined using chi-square tests and logistic regression analysis.

Results: Chi-square tests reveal that the following factors show significant correlation with the manifestation of learning disorders: gender (male), maternal complications during pregnancy, perinatal complications, medical record of acute and chronic organic diseases and absence of breastfeeding. A high prevalence of learning disorders has been found in children aged 6-9 and in adolescents aged 12-18 years, whereas prevalence is low in cases in which the educational level of the mother or of both parents is high. Acute diseases show the strongest positive correlation with learning disorders (odds ratio: 17.65), followed by chronic diseases (odds ratio: 12.76).

Discussion: In the present study boys are three times more often affected by learning disorders than girls (76.90% against 23.10%), which is consistent with previous findings in the literature. To some extent, differences may be caused by biological factors but there are investigators who attribute these differences to biased referral practices by schoolteachers, in which boys with disruptive behavior are preferentially referred for assessment. In our sample, the highest prevalence of learning disorders was found in the age range of 6-9 and 12-18. As far as incidence in childhood is concerned, it is assumed that fluctuations in the prevalence rates in the different grades may partly be explained by variations in the rate of early literacy acquisition, with highest rates at the age of 8 years. The high academic demands later on combined with excessive parental expectations regarding academic achievement, may account for the high prevalence rates observed in adolescence. Maternal complications during pregnancy as well as perinatal complications seem to increase the incidence of learning disorders according to our findings. This lends support to the theory (Galaburda, A., 1994) that dyslexia is a neurodevelopmental disorder, accompanied by fundamental changes in brain anatomy and physiology, which can be attributed to abnormal prenatal and immediately postnatal brain development. The absence of breastfeeding might also have a negative impact on early development, although in our study it was not specified whether the causes were related to the child or the mother. A strong correlation was found between learning disorders and acute recurrent organic diseases. The latter can lead to negative impact on educational progress due to: a) frequent absence from school, b) lack of child motivation for scholastic achievement, since parental concerns focus on health problems rather than on school progress and c) fatigue caused by sleep apnea as a result of adenoid or tonsil overgrowth. Chronic diseases such as juvenile diabetes or asthma, which tend to be attributed to some extent to immunological causes, show the second strongest correlation with learning disorders in our study. This is in concordance with studies, which report higher incidence of immune disorders in dyslexic populations. The findings support the theory proposed by Geschwind-Behan-Galaburda (1984) on the existence of a common underlying (most probably genetic) factor among dyslexia, immune disorders and handedness. Finally, it appears that social factors such as the high educational level of the parents have a positive effect in the school progress of their children. Most studies report a positive correlation between learning disorders and low parental socioeconomic or academic status. Research conducted in our Department does not support these findings.

Conclusion: The present study shows that both biological and social factors contribute to the manifestation of learning disorders, which is in accordance with the bio-psycho-social model of psychiatric disorders.

Key words: Learning disorders, organic diseases, social factors.