Depression is a serious mental illness which affects one in five of us at some point in our lives. Symptoms can vary from mild to feeling suicidal.
Sometimes there's an identifiable cause for depression, such as a stressful life event like bereavement, work pressures, and debt or divorce, but sometimes there isn't an obvious trigger.
Experts say depression can be caused by a combination of factors including stressful events, individual personality traits, a family history, illness, loneliness, giving birth, head injuries, drinking too much alcohol and drug abuse.
Feeling sad or tearful, guilty, worthless, hopeless, fatigued and having no self-confidence are common symptoms of depression.
Some people no longer get pleasure out of things they have previously enjoyed, can't sleep (or sleep too much), lack concentration, lose their appetite and sex drive, become restless and/or deliberately avoid social events and isolate themselves.
The most extreme symptom that should never be ignored is feeling suicidal.
Your doctor will ask you questions about your mood, thoughts and feelings, as well as giving you a self assessment questionnaire to fill out. This will help them come to a diagnosis, understand the severity of your illness, and decide on the best course of treatment.
Who gets it?
This is important to remember: anyone can develop depression.
Family history is perhaps one of the biggest risk factors associated with the illness, as having a sibling or parent with a history of depression can make you up to three times more likely to develop it yourself.
Some life events such as divorce or bereavement carry a greater risk of triggering depression. However, not everyone who has these life experiences will go on to develop depression, and not everyone who develops depression will have these experiences.
Women are reported to be twice as likely to develop depression than men, but this could be because men tend to leave it longer to get help. This is reflected in the higher suicide rates in men, in 2014 the suicide rate for men in the UK and the Republic of Ireland was 16.8 per 100,000 compared to 5.2 per 100,00 in women.
Around one in ten women who give birth develop post-natal depression. You are more prone to this if you have a family or personal history of depression, lack a support network, have financial / relationship problems, or your baby has special needs.
Other at-risk groups include people aged over 65 and around 28 per cent of women and 22 per cent of men experience depression in this age group. People who have experienced bullying or discrimination, had a long-term physical illness or another mental illness such as an eating disorder or anxiety, are also at higher risk .
Treatment will depend on the severity of your symptoms. Options available on the NHS include psychological therapies and drug treatments and you may be offered a combination of both.
Cognitive Behavioural Therapy (CBT) is a type of 'talking' therapy that attempts to change how we think and act in certain situations, which has been found to significantly reduce symptoms of depression in up to 46 per cent of cases.
Talking therapies including counselling, group therapy and a newer approach called mindfulness which teaches people to pay attention to the present moment, all of which have been shown to be effective treatments in people suffering with depression.
Antidepressants are prescribed for moderate to severe depression. Selective serotonin re-uptake inhibitors (SSRIs) are the newer and most common type of antidepressant prescribed in the UK, they work by increasing serotonin a 'feel-good' brain chemical.
St John's Wort is a popular herbal remedy for mild to moderate depression, but should not be taken with antidepressants (as well as a number of other medications), as it can cause serious side effects.
A diet rich in B vitamins and omega 3 fatty acids has also been found to be important in preventing depression.Taking exercise lifts your mood by boosting 'feel good' endorphins and combats symptoms such as fatigue and poor sleep.