Learning problems

A national Swedish study involving the 1.16 million children in a national birth cohort identified nearly 8000 on the country's Prescribed Drug Register as using a prescription for ADHD medication (and thus assumed to suffer from severe ADHD). These children were significantly more likely to come from a family on welfare benefits (135% more likely), to have a mother with only the most basic education (130% more likely than those with mothers with university degrees), and to come from a single parent family (54% more likely).

Data from the same long-running study (the NICHD Study of Early Child Care and Youth Development), this time involving 1,364 youth (followed since birth), found that teens who had spent the most hours in non-relative child care in their first 4½ years reported a slightly greater tendency toward impulsiveness and risk-taking at 15 than did peers who spent less time in child care (21% were in care for more than 30 hours a week; 24% had had more than one year of care by 4 ½).

A rat study shows how Ritalin improves concentration and, it now appears, speed of learning. The study reveals that it does this by increasing the activity of dopamine at two specific types of neurotransmitter receptors in the amygdala. The dopamine receptor tagged “D2” appears to control the ability to stay focused on a task, while the D1 receptor underlies learning efficiency. The finding may help the development of better-targeted drugs.

An imaging study has revealed that children (aged 5-15) whose mothers abused methamphetamine and alcohol during pregnancy had structural abnormalities in the brain that were more severe than those seen in children whose mothers abused alcohol alone. In particular, the striatal region was significantly smaller, and within the group, size of the caudate correlated negatively with IQ. Limbic structures, in particularly the cingulate cortex and the right inferior frontal gyrus, were significantly bigger.

When a pregnant woman uses cocaine, it can interrupt the flow of nutrients and oxygen to the baby, putting such children at risk for premature birth, low birth weight and many other problems. However a new review of 32 major studies of school-age children reveals that the consequences for the brain are less sweeping than feared. Although many of the children did have low IQ and poor academic and language achievement, this seems to be related more to the home environment.

Supporting the idea that repeated anaesthesia in children can lead to memory impairment, a rodent study has revealed that repeated anaesthesia wiped out a large portion of the stem cells in the hippocampus. This was associated with impaired memory in young animals, which worsened as they got older. The effect did not occur in adult animals. A similar effect has also been found with radiotherapy, and animal studies have found physical activity after radiotherapy results in a greater number of new stem cells that partly replace those that have been lost.