There is no single cause of depression, and people develop depression for different reasons. Depression has many different triggers.
There is no single cause of depression. You can develop it for different reasons and it has many different triggers.
For some, an upsetting or stressful life event – such as bereavement, divorce, illness, redundancy and job or money worries – can be the cause.
Often, different causes combine to trigger depression. For example, you may feel low after an illness and then experience a traumatic event, such as bereavement, which brings on depression.
People often talk about a "downward spiral" of events that leads to depression. For example, if your relationship with your partner breaks down, you're likely to feel low, so you stop seeing friends and family and you may start drinking more. All of this can make you feel even worse and trigger depression.
Some studies have also suggested you're more likely to get depression as you get older, and that it's more common if you live in difficult social and economic circumstances.
Most people take time to come to terms with stressful events, such as bereavement or a relationship breakdown. When these stressful events happen, you have a higher risk of becoming depressed if you stop seeing your friends and family and you try to deal with your problems on your own.
Head injuries are also an often under-recognised cause of depression. A severe head injury can trigger mood swings and emotional problems.
Some people may have an underactive thyroid (hypothyroidism) resulting from problems with their immune system. In rarer cases a minor head injury can damage the pituitary gland, a pea-sized gland at the base of your brain that produces thyroid-stimulating hormones.
This can cause a number of symptoms, such as extreme tiredness and a loss of interest in sex (loss of libido), which can in turn lead to depression.
You may be more vulnerable to depression if you have certain personality traits, such as low self-esteem or being overly self-critical. This may be because of the genes you've inherited from your parents, or because of your early life experiences.
If someone else in your family has suffered from depression in the past, such as a parent or sister or brother, then it's more likely you will too.
Some women are particularly vulnerable to depression after pregnancy. The hormonal and physical changes, as well as added responsibility of a new life, can lead to postnatal depression.
Becoming cut off from your family and friends can increase your risk of depression.
Alcohol and drugs
Cannabis helps you relax, but there is evidence that it can bring on depression, especially in teenagers.
And don't be tempted to drown your sorrows with a drink. Alcohol is categorised as a "strong depressant" and actually makes depression worse.
See your GP if you think you have depression. Your GP may give you a physical examination and do some blood or urine tests to rule out other conditions.
If you experience symptoms of depression for most of the day, every day for more than two weeks, you should seek help from your GP.
It is especially important to speak to your GP if you experience:
symptoms of depression that are not improving
your mood affects your work, other interests, and relationships with your family and friends
Sometimes, when people are depressed they find it hard to imagine that treatment can actually help. But the sooner you seek treatment, the sooner your depression will lift.
The main way in which your GP will tell if you have depression is by asking you lots of questions about your general health and how the way you are feeling is affecting you mentally and physically.
Try to be as open as you can be with the doctor. Describing your symptoms and how they are affecting you will really help your GP understand if you have depression and how severe it is.
Read more about the symptoms of depression.
Any discussion you have with your GP will be confidential. Your GP will only ever break this rule if there's a significant risk of harm to either yourself or others, and if informing a family member or carer would reduce that risk.
Find out about the treatments you may be offered for depression.
Vanessa Phillips from Hertfordshire was known as a strong person, always willing to help others. When she had a breakdown, her friends didn’t know she needed help.
Vanessa Phillips from Hertfordshire was known as a strong person, always willing to help others. When she had a breakdown, her friends didn't know she was the one who needed help.
"My breakdown was triggered by my mother's death. I was a 41-year-old divorced single parent of two children and I had no support. The council was trying to evict me from my home.
"I was eating hardly anything and I wasn't sleeping. I was shaking and suffering huge anxiety, but I didn't know I was ill. I thought I just had too much on my plate. I now feel that if people had been there for me, if people had listened to me, I might not have become so ill.
"Everyone knew me as a very strong person who helped others with their problems, so when I was saying, 'I'm not coping, I need help', people didn't pay any attention. I began spending a lot of time in bed under my duvet. I went to my doctor, who gave me antidepressant pills. I knew nothing about depression and he didn't tell me anything.
"A friend came round to see if I was all right one Friday morning. She didn't know I'd already decided to kill myself. She found me sitting in bed ranting and raving. She saw an empty pill bottle and a half-empty bottle of whisky and she phoned my doctor, who called an ambulance.
"I was kept in hospital for two weeks and sent home with more pills, but still no more information about depression. I started going to the library and reading books on mental health, and saw how diet, lifestyle, healthy eating and vitamins were involved.
"Slowly, I began to recover. I had a lot of help from a lovely mental health nurse who took a real interest in me. She used my love of plants to deal with my social exclusion by driving me in her car to the garden centre for a walk and a cup of coffee. Having someone else caring about me was the catalyst that helped me sort out things I couldn't cope with.
"It took me a long time, but I got back on my feet. It would have been faster if I'd had more support and more information. I now run a depression awareness group so that other people don't have to go through what happened to me."
Lawrence has depression. He explains how easy it was to ignore the symptoms, despite being a psychiatric nurse, and the problem this caused his working life.
Lawrence has depression. He explains how easy it was to ignore the symptoms, even though he is a psychiatric nurse, and the problem this caused in his working life.