An interesting new study has emerged that shows low levels of antidepressants and other psychoactive drugs in water supplies can trigger the expression of genes associated with autism – in fish at least.
Pharmaceuticals In Our Water Supply?
The use of antidepressants has increased dramatically over the past 25 years, says Michael Thomas of Idaho State University in Pocatello. Around 80 per cent of each drug passes straight through the human body without being broken down, and so they are present in waste water. In most communities, water purification systems cannot filter out these pharmaceuticals. “They just fly right through,” says Thomas, which means they ultimately find their way into the water supply.
The concentration of these drugs in drinking water is very low – at most, they are present at levels several orders of magnitude lower than the prescription doses. But since the drugs are specifically designed to act on the nervous system, Thomas hypothesized that even a small dose could affect a developing fetus.
Thomas’s group created a cocktail of the anti-epileptic drug carbamazepine and two selective serotonin uptake inhibitor (SSRI) antidepressants, fluoxetine and venlafaxine, at this low concentration. They exposed fathead minnows (Pimephales promelas) to the drugs for 18 days, then analysed the genes that were being expressed in the brains of the fish that were studied.
324 Genes Associated With Autism
Although the researchers had expected the drugs might activate genes involved in all kinds of neurological disorders, only 324 genes associated with autism in humans appeared to be significantly altered. Most of these genes are involved in early brain development and wiring.
The finding fits with previous research which had found that pregnant women who take are slightly more likely to have autistic children.
To test whether these changes actually altered the fish’s behaviour, the researchers did an experiment in which they startled the fish. Fish exposed to the drugs tended to panic and behave differently from a control group of fish.
Study Results Are Preliminary
The study doesn’t come close to proving that trace levels of SSRI antidepressants in drinking water cause autism and Thomas emphasises that the research is very preliminary – there’s no need for pregnant women to worry about their drinking water yet, he says. The researcher’s next plan is to study whether the drugs have a similar effect in mammals. They are testing this by lacing the drinking water of pregnant mice with the low-concentration cocktail. They are also studying water supplies in areas around the country where there are particularly high concentrations of drugs to determine whether the fish – and people – in these areas have autism-like gene expression patterns.
This is not the first time research has linked the use of SSRI antidepressants to autism. In fact, a study published in Archives of General Psychiatry this past July, children born to mothers who took an SSRI in the year before pregnancy faced a two-fold increased risk of being diagnosed with an Autism Spectrum Disorder (ASD). The risk jumped to nearly four-field if an expectant mother took an SSRI antidepressant in the first trimester of pregnancy.
The study was published in the journal PLoSOne.