All popular perspectives (e.g. those focusing on brain structure and functioning, early childhood experiences, cognitive development, peer influences, sleeping arrangements, interaction with environment, etc) fall in one of these groups, though each deals with a specific aspects of either 'nature' or 'nurture'.
The balance between the two stances is different for each disorder and inevitably changes over time. Thus, the recent research of children with ADHD disorder finally rebutted the previously popular theory of the 'minimal brain damage' (Swanson et. al., 1998). Instead, the advances in genetic engineering and technology allowed more accurate and comprehensive research of genes allegedly responsible for ADHD and led to identification of two genes: a dopamine-receptor (DRD) gene on chromosome 11 and the dopamine-transporter gene (DAT1) on chromosome 5 (US Public Health Service, 2000). The genetic research revealed clear evidences that children with ADHD have genetic variations in one of the dopamine-receptor genes, namely DRD4. Many studies report that abnormalities of the dopamine-transporter gene (DAT1) have been present in children and adolescents with especially severe forms of ADHD (US Public Health Service, 2000). Nutritional factors, glucose levels and other new determinants are linked to this disorder in the modern research.
Similarly, the aetiology of bipolar disorder, another commonly met childhood disorder is also explained from a number of perspectives. Studies involving twins and relatives demonstrate that bipolar disorder tends to run in families. However, the search for specific genes responsible for the disorder failed because studies of identical twins, who obviously possess the same genetic structure, rebutted the notion of genetic structure as the sole cause (NIMH, 1998.).
Bipolar disorder is a mental disease that is why brain-imaging studies seem to be of great help in learning what exactly goes wrong in the brain and causes bipolar illness as well as other mental disorders. Contemporary methods and advanced techniques make possible having a picture of the living and working brain without destructive procedures, like surgery for instance. Magnetic resonance imaging, positron emission tomography and other techniques really helped to find out that the brains of persons with some form of bipolar illness really differed from the brains of normal people (Soares & Mann, 1997).
The following physiological factors, detected with the help of the contemporary techniques, are called among the causes of bipolar disorders:
- Excessive secretion of cortisol, a hormone that controls stress;
- Excess of calcium in brain cells;
- Abnormal hyperactivity in those parts of brain that are responsible for emotions and motor activity accompanied with low activity of those parts responsible for attention, logic, and concentration