When I was little I visited some incredible caves in central Italy – the Grotte di Frasassi. I was a bit of a nervous child, and walking down into the dark through a huge tunnel carved out of solid rock was pretty scary. I was happier when the caverns opened up inside, into a space bigger than St Paul’s cathedral and filled with stalactites and stalagmites.
The thing I remember most clearly is a scary story the guide told us, about a group of monks who had become hopelessly lost inside the caves. They tried to trace their way back out by running their hands along the walls of the passages in the rock, but after days and days they still hadn’t escaped, and their fingers had worn down to the bone. Luckily I wasn’t quite little enough to believe this, but I still felt very relieved when we walked out into the sunshine again.
You certainly don’t have to go underground to feel the mood-enhancing effects of sunshine. January in London is a pretty dismal month, especially if you’re getting up when it’s still dark. So a few sunny days in the past couple of weeks have really cheered me up – I can almost feel the corners of my mouth twitching when the sun comes out.
This isn’t just about my mood. The bright light is affecting my brain directly, through special cells in my retina. The cells send signals to an area of the brain called the suprachiasmatic nucleus, and from here signals travel on to the pineal gland. This tiny gland secretes melatonin, the hormone that controls the body’s rhythms, regulating everything from the activity of enzymes in the liver to processes in the brain.
The discovery of the specialised cells in the retina was a bit of a surprise – for years scientists believed that the same cells we need to see were also doing the job of regulating our circadian rhythms. But a group led by Professor Russell Foster at the University of Oxford proved this theory to be wrong. They found a whole new set of light-sensitive neurons, and they’re continuing to investigate these intriguing cells.
So sunlight is one external stimulus that helps sychronise our internal clocks to the world around us. Our circadian rhythms are on a cycle that’s a little longer than 24 hours, so cues like sunshine and darkness help reset them to keep us on track. This is why jet lag and dark mornings can be a problem – we’re not getting the day and night reminders that we need.
But although jet lag and the winter blues can be seriously annoying, they’re not usually a life or death issue. I was quite shocked to discover just how much we really can be affected by our circadian rhythms.
A few years ago I heard a lecture given by Professor Russell Foster, discoverer of those interesting neurons in the eye. He explained circadian rhythms and how they control almost every aspect of our lives. For example, there is more and more evidence that the time at which a person takes a drug can make a huge different to the drug’s effect. And we’re not just talking about ‘recreational’ drugs here. What if the timing of taking a cancer drug had an effect on the treatment’s success?
One study in 2008 found that side effects from certain cancer drugs were up to five times more frequent at the ‘worst’ times than the best times for giving the drug. And even more importantly, some drugs were more than twice as effective at shrinking the cancer if given in the ‘best’ rather than ‘worst’ timeslots.
The idea is that drugs will work best when healthy cells are least active, so they are protected from damage. Because cancer cells are growing out of control, they should be more continuously active and so more affected by the drugs. But research in this area hasn’t got very far, so we still don’t know for sure when patients should be treated to get the best result. And because very cancer is different, it’s possible the best time for one patient could be not nearly as good for another.
Professor Foster also pointed out that timing has a huge effect on the brain. He said that a person trying to stay awake and function in the middle of the night, around 3 or 4am, is comparable to someone who is drunk. Their brain function is quite seriously impaired by a dip in brain activity because of their circadian rhythms. His tip was, don’t drive at these times!
Some of Professor Foster’s latest research is focusing on schizophrenia – and it turns out that circadian rhythms have a huge effect on this condition too. People with schizophrenia often suffer from sleep disturbance, and this problem makes their psychotic symptoms worse. Professor Foster and his team have found that schizophrenics have abnormal circadian rhythms, which are either delayed or completely independent of the time of day. They hope that by uncovering exactly how and why these rhythms are faulty they may be able to shed more light on the condition, and perhaps even find clues for new treatments.
There’s more and more evidence to show that timing really is everything when it comes to the body. So next time I feel my mood lift when the sun comes out, I’ll try and remember how powerful that feeling really is.