Anxiety gene turns out a bit of a worry

It's all rather worrying really. Last year scientists in the US and Germany announced they had found an "anxiety" gene - which played a part in determining how anxious people were, according to psychological tests measuring a trait called "harm avoidance".

But now another team of scientists, based in Jerusalem, say that direct measurement of 120 people with and without that gene showed no correlation between their anxiety levels and the gene's presence.

So is it worrying that the anxiety gene appears to have disappeared? According to one author of the latest study, Richard Ebstein of the Sarah Herzog Memorial Hospital, it may only mean that the gene affects anxiety in some groups but not others; and one of the authors of the original study suggested that the latest project would not have detected the effect anyway.

But significantly, this is the second time since November that a follow- up study for a "personality gene" has failed to find it. Ironically, the previous failure was trying to confirm a finding claimed by Dr Ebstein - that there is, or was, a gene for "novelty-seeking", including excitability and impulsiveness.

Claims in 1995 that there is a "gay gene" on the X chromosome have also not been confirmed by later studies.

Dean Hamer of the National Cancer Institute, one author of last year's study - and also a co-author of the original "gay gene" paper - said Dr Ebstein's result was meaningless because it used too few people. The original study investigated 505 people using three psychological tests, whereas the new one, published this month in Molecular Psychiatry, only looked at 120.

According to Dr Hamer, even with the 505 people in last year's study the effect was barely noticeable. Dr Ebstein commented: "There is now some element of doubt [about the original study] but it doesn't mean they're wrong." Differences in genetic backgrounds and environment could mean the gene influences the anxiety trait differently in some groups.

The gene itself lies on chromosome 17 and plays a role in a brain communication system that takes the neurotransmitter serotonin - the "pleasure chemical" - back into brain cells. The gene itself comes in two forms, "short" and "long", so it seemed logical the short version would lead to less available serotonin - and so more readily to a state of anxiety. But Dr Ebstein said he couldn't find the least sign of the effect in his group.

Body Clock ticks on

Genes help us to tell the time by keeping our "circadian clock" running, new research has shown.

American researchers have discovered the functions of two genes which may explain how almost every organism on Earth has a built-in ability to monitor time on a 24-hour, day-to-night basis - even when kept in complete darkness.

The first gene seems to act as an independent timer, like a clockspring; the other is in effect a gear cog which keeps the clock running.

The team found clock malfunction was linked to seasonal affective disorder and various sleep and mental disorders.