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Increased rainfall, or something linked to it, may be connected to the development of autism, scientists say.

The theory is based on child health and weather records from three US states, but has been greeted cautiously by a UK research charity.

The US study found autism rates were higher among children whose states experienced higher rainfall in their first three years.

The work appears in Archives of Pediatrics and Adolescent Medicine.

The rising rate of autism - up, by some measures, from one in 2,500 to one in 150 - has been attributed mainly to improvements in the way doctors are able to recognise the disorder.

However, scientists from Cornell University say this does not exclude a factor which may be independently increasing the number of children growing up with the condition.

They calculated average annual rainfall for California, Oregon and Washington State between 1987 and 1999, then looked at autism prevalence rates in the children growing up during this period.

They found that rates could be linked to that amount of precipitation in their state between these dates.

They added: "Autism prevalence was higher for birth cohorts that experienced relatively heavy precipitation when they were younger than three years."

The reason for the link, if it exists, might not be directly related to rainfall, although the scientists said it was possible that the process of rainfall might affect the chemicals to which children were exposed.

Indoor theory

They also suggested that being forced to stay indoors for longer periods could affect development, perhaps by increased exposure to television, or to household chemicals, or even through a lack of vitamin D, produced by being out in sun.

However, they made it clear that none of these was more than a theory, and called for further research to see if the link was a real one.

Mark Lever, chief executive of The National Autistic Society said the latest theory would join a succession of others advanced about the condition and its origins.

He said: "In recent years autism has been linked to factors as varied as older aged fathers, early television viewing, vaccines, food allergies, heavy metal poisoning, and wireless technology, to name just a few.

"Some of these theories are little more than conjecture or have been discredited, others seem more promising and are in need of further study. As yet, however, very few have been substantiated by scientific research."

He said: "We don't yet understand what causes autism, although scientists do believe that genetic factors might play a part.

"People with autism and their families are naturally concerned to get the right information and there is a lot of confusion and concern over the conflicting theories put forward."

autism自我中心主義;我向思考  孤獨症

cautiously 小心地,謹慎地

Archives 檔案館,檔案保管處;資料庫

Pediatrics 小兒科

Adolescent 青少年 青少年的;幼稚的,未成熟的

attributed 把...歸因於;把...歸咎於

recognise 認出,識別;認識  正式承認;認可,認定

disorder混亂,無秩序  騷亂,動亂[

exclude 拒絕接納;把...排除在外;不包括

independently 獨立地,自立地;無關地

calculated 預先計劃的;可能的

annual 每年的;全年的

prevalence 流行,盛行;普遍,廣泛   (疾病等的)流行程度

precipitation

cohorts 一隊人;一群人

executive 行政上的;行政部門的

succession 連續,接續

vaccines牛痘的;疫苗的

allergies厭惡,反感  過敏症

conjecture 推測,猜測;推測的結果

discredited使丟臉;敗壞...的名聲 不信,懷疑

promising 有希望的,有前途的,大有可為的

substantiated 證實,證明...有根據

conflicting 相矛盾的;衝突的