Scots experts shine light on mystery of SAD sufferers

Published on Thursday 29 April 2010 23:11

SCOTTISH scientists are hopeful they have made a key step towards creating new treatments for the so-called "winter blues".

• Intensive light treatment is currently used to treat symptoms of seasonal affective disorder. Picture: TSPL

The researchers have discovered two "body clock" genes that reveal how seasonal changes in hormones are controlled.

Eventually, it is hoped that the findings could help lead to new ways to tackle seasonal affective disorder (SAD) – a form of depression suffered during the winter months.

About 7 per cent of people in Scotland are estimated to experience SAD, with many more having a milder version of the winter blues.

Researchers at the universities of Edinburgh and Manchester have been investigating how genes affect changes in the body caused by the seasons.

One of the genes they found linked to seasonal changes in hormones – known as EYA3 – also had a similar role in both birds and mammals, which they said showed a common link that has been conserved for more than 300 million years.

The scientists studied thousands of genes in Soay sheep.

This breed, which dates back to the Bronze Age, is considered to be one of the most primitive, with seasonal body clocks unaffected by cross-breeding throughout the centuries.

Scientists have long speculated that a key molecule – called tuberalin – was produced in the pituitary gland at the base of the brain and sent signals to release hormones involved in driving seasonal changes.

Until now, however, they had no idea about the nature of this molecule, how it worked or how it was controlled.

The team in Edinburgh and Manchester focused on a part of the brain that responds to melatonin – a hormone known to be involved in seasonal timing in mammals.

The study found a molecule suspected to be tuberalin, which communicates within the pituitary gland to signal the release of another hormone – prolactin – when days start getting longer.

This helps animals adapt to seasonal changes in the environment.

The researchers, whose findings are published in the journal Current Biology, subsequently identified two genes – TAC1 and EYA3 – that were both activated early when natural hormone levels rise due to longer days.

Professor Dave Burt, from the Roslin Institute at Edinburgh, said: "For more than a decade, scientists have known about the presence of this mysterious molecule tuberalin, but until now nobody has known quite how it worked.

"Identifying these genes not only sheds light on how our internal annual body clocks function but also shows a key link between birds and mammals that has been conserved over 300 million years."

The discovery of the genes gives researchers a new target to explore to find treatments for SAD.

Professor Andrew Loudon, from Manchester's Faculty of Life Sciences, said: "A lot of our behaviour is controlled by seasons. This research sheds new light on how animals adapt to seasonal change, which impacts on factors including hibernation, fat deposition and reproduction as well as the ability to fight off diseases."

FEELING GLUM

SEASONAL Affective Disorder is a type of winter depression.

It is thought to be caused by lack of light in the darkest months of the year.

Symptoms include feeling depressed and anxious, problems sleeping, overeating and food cravings as well as lethargy.

Research indicates that concentrating on increasing light exposure using artificial "light boxes" can help.