A common variation in a gene for an immune system protein increases a child’s risk of developing Attention Deficit Hyperactivity Disorder (ADHD) by 30 per cent, say Israeli researchers.

ADHD affects between four and 10 per cent of school age children and is characterised by inattention, hyperactivity and impulsivity. The causes are unknown. But stimulant drugs such as Ritalin, which boost levels of the neurotransmitter dopamine, have been shown to reduce symptoms in many patients. 

Other researchers have also found evidence linking ADHD to variations in certain genes exclusively involved in the dopamine system.

Ronen Segman of the Hadassah-Hebrew University Medical Center in Jerusalem and colleagues studied 86 families with children diagnosed with ADHD. They found a significant association between a variation in the gene for the immune system protein interleukin-1 (IL-1) and ADHD.

IL-1 is involved in the immune inflammatory response. But recent work has shown that it also has other roles in the body. IL-1 helps control the release of dopamine and another neurotransmitter called norepinephrine in several brain regions. It also helps promote the growth of dopamine-producing brain cells in the developing embryo.

“If replicated, these findings point to the importance of immune factors acting as neuromodulators,” Segman told New Scientist. “This might form a basis for future new interventions for ADHD based on neuroimmune modulation.”

However, the causes of ADHD are complex, he adds. “A number of environmental factors such as maternal smoking, high levels of family problems and emotional stress during pregnancy have also been linked with the risk for ADHD.”

Journal reference: Molecular Psychiatry (vol 7, p 72)

Written by Emma Young, and published on DrKelley.info, January 6, 2002. Embedded links (if any) may no longer be active. (Ed. 12.31.10)

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