Depression is a common illness. According to the World Health Organization, more than 350 million people suffer from it worldwide. But what happens in our brains when we feel unhappy?
Highly detailed MRI (magnetic resonance imaging) scans show areas of the brain literally lighting up when a person thinks about certain subjects.
For example, when they think about playing tennis, the same areas of the brain are activated as when they actually play the game.
This mapping of brain activity is invaluable in developing our understanding of how the brain works.
Neuroscientists have discovered that one of the areas of the brain most involved in mood control is the cingulate cortex, an inner layer of the brain.
When a sad - or possibly depressed - person was scanned, the front of the cingulate cortex was found to be very active and the back showed a reduction in activity. These findings were reversed in patients who had emerged from depression.
Further studies and research will reveal more about depression and its causes. But the issue provides a starting point for discussing how anti-depressant drugs and other therapies can influence our moods.
Help students to cope with bereavement using guidance from NHS Choices. bit.lynhschoices
Television presenter and Lord Byron fan Miquita Oliver talks about the poet in this video from BBC Learning. bit.lyoliverbyron
How do scientists know what happens in the brain? This magazine from Wellcome Trust contains information on imaging techniques. bit.lybrainmag
In Looplou13's lesson on happiness, students learn how setting "SMART" goals can help us to feel happy. bit.lymentalwellbeing.