What is depression?
Depression is very common, affecting about one in every 20 people at some point in their lives. It is thought to be caused by inadequate activity of neurones that release serotonin or noradrenaline, which results from a combination of inherited and environmental factors. Short daylight hours in winter trigger one type of depression - seasonal affective disorder (SAD), while postnatal depression can affect mothers during the first year after giving birth.
