There are several ideas about what causes depression. It can vary a lot between different people, and for some people a combination of different factors may cause their depression. Some find that they become depressed without any obvious reason.
In this section you can find information on the following possible causes of depression:
Is depression caused by a chemical imbalance?
The human brain is extremely complicated. Because antidepressants work by changing brain chemistry, some people have assumed that depression is caused by changes in brain chemistry which are then ‘corrected’ by the drugs. Some doctors may tell you that you have a ‘chemical imbalance’ and need medication to correct it.
But the evidence for this is very weak, and if changes to brain chemistry occur, we don’t know whether these are the result of the depression or its cause.
There is good evidence to show that going through difficult experiences in your childhood can make you vulnerable to experiencing depression later in life. This could be:
- physical, sexual or emotional abuse
- the loss of someone close to you
- traumatic events
- an unstable family situation.
Research shows that going through lots of smaller challenging experiences can have a bigger impact on your vulnerability to depression than experiencing one major traumatic event.
Difficult experiences during your childhood can have a big impact on your self-esteem and how you learned to cope with difficult emotions and situations. This can make you feel less able to cope with life's ups and downs, and lead to depression later in life.
NAPAC support anyone who experienced abuse in childhood – including sexual, physical and emotional abuse, and neglect.
I first experienced depression at 15, after psychological abuse and domestic violence (both myself and my mother) at the hands of my father, for many years.
In many cases, you might find your depression has been triggered by an unwelcome, stressful or traumatic event. This could be:
- losing your job or unemployment
- the end of a relationship
- major life changes, like changing job, moving house or getting married
- being physically or sexually assaulted
- being bullied or abused.
I started to feel that depression really took a hold after a torrid time in my job, where I was bullied – I just crumbled.
It’s not just negative experiences that cause depression, but how we deal with them. If you don't have much support to help you cope with the difficult emotions that come with these events, or if you're already dealing with other difficult situations, you might find that a low mood develops into depression.
My depression seems to flare up during times when I am stressed and isolated from other people.
When does grief become depression?
Grief, and the low mood that comes with it, is a natural response to losing someone or something we love. How long your grief, or bereavement, lasts will be individual to you. This period of feeling low is referred to as bereavement.
But if you feel that what you're experiencing might be something more than just grief, you can talk to your doctor about it.
You might want to try bereavement counselling first, as this may be more helpful for you than general treatment for depression. Cruse Bereavement Care offers support and counselling for anyone affected by bereavement.
For me, it started when my mother died. After struggling and burying things deeper, I finally cracked.
Other mental health problems
If you experience another mental health problem, it's common to also experience depression. This might be because coping with the symptoms of your mental health problem can trigger depression. You may find you experience depression if you also experience:
Physical health problems
Poor health can contribute to your risk of developing depression. Many health problems can be quite difficult to manage, and can have a big impact on your mood. These could be:
- chronic (long-term) physical health problems
- life-threatening physical illnesses
- physical health problems that significantly change your lifestyle.
You might be offered support for your mental health at the same time as you are treated for a physical health problem, as part of your overall treatment.
There are some physical health problems that can cause depression:
- conditions affecting the brain and nervous system
- hormonal problems, especially thyroid and parathyroid problems
- symptoms relating to the menstrual cycle or the menopause
- low blood sugar
- sleep problems.
If you think any of the above conditions apply to you, make sure your doctor knows about them. Some can be diagnosed by simple blood tests – your doctor may suggest these are done to help make the right diagnosis, or you can ask for blood tests if you think they may be relevant.
Although no specific genes for depression have been identified, research has shown that if you have a close family member with depression, you are more likely to experience depression yourself.
While this might be caused by our biology, this link could also be because we usually learn behaviour and ways of coping from the people around us as we grow up.
Medication, recreational drugs and alcohol
Depression can be a side effect of a lot of different medicines. If you are feeling depressed after starting any kind of medication, check the patient information leaflet to see whether depression is a side effect, or ask your doctor. If you think a drug is causing your depression, you can talk to your doctor about taking an alternative, especially if you are expecting your treatment to last some time.
Alcohol and recreational drugs can both cause depression. Although you might initially use them to make yourself feel better, or to distract yourself, they can make you feel worse overall. See our pages on the mental health effects of recreational drugs and alcohol for more information.
Sleep, diet and exercise
A poor diet and lack of sleep and exercise can affect your mood, and make it harder for you to cope with difficult things going on in your life.
Although a poor diet, or not getting enough sleep or exercise, cannot directly cause depression, they can make you more vulnerable to developing it.
See our pages on food and mood, sleep problems and physical activity for more information.
This information was published in March 2019. We will revise it in 2022.