What causes depression?

Depression varies very much from person to person and can happen for one or more reasons. Occasionally it may appear for no obvious reason.

Life events

In many cases, the first time someone becomes depressed, it has been triggered by an unwelcome or traumatic event, such as being sacked, divorced, or physically or sexually assaulted.


Often events or experiences that trigger depression can also be seen as a loss of some kind. It could be following the actual death of someone close, a major life change (such as moving house or changing jobs), or simply moving from one phase of life into another, e.g. as you reach retirement, children leave home, or you come to realise that you may never have a family of your own.

It’s not just the negative experience that causes the depression, but how we deal with it. If the feelings provoked are not expressed or explored at the time, they fester and contribute towards depression.


In some cases some people call depression ‘frozen anger’. You may have experienced something which left you feeling angry and helpless, and if you were unable to express your feelings at the time – perhaps because you were a child, or your feelings were unacceptable to others – the anger becomes internalised and is expressed as depression.

Childhood experiences

If you experienced a traumatic event in childhood, or were abused physically or emotionally, or were not helped to learn good coping skills as you grew up, this can leave you less able to cope with difficulties as an adult.

Physical conditions

The following conditions may cause depression, but are sometimes overlooked because of the focus on their physical symptoms:

  • Conditions affecting the brain and nervous system
  • Hormonal problems, especially thyroid and parathyroid problems
  • Symptoms relating to the menstrual cycle or 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 of these problems can be diagnosed by simple blood tests, and your doctor may suggest that these are done to help make the right diagnosis, or you can ask for blood tests if you think they might be relevant for you.

Side effects of medication

Depression is a side effect of a lot of different medicines; for example, many people become depressed after a heart attack, and this may be more likely if they are taking beta blocker medicines as part of their treatment.

If you are feeling depressed after starting any kind of medication, it’s worth looking at the patient information leaflet that came with the drug to see if depression is listed among the side effects. If you think a drug is causing your depression, you could mention this to your doctor and see if there is an alternative you could take, especially if you are expecting the treatment to last some time.


Poor diet and general lack of fitness can both contribute to depression.

In addition, anecdotal evidence suggests that occasionally people become very depressed in response to some specific foods. Such a reaction is very individual, and people are often not aware of the particular food substance or drink that is causing the problem.

But if you suddenly feel depressed for no apparent reason, it may be worth considering whether you have eaten or drunk something new, and whether this might have caused your sudden change of mood. If this is the cause, your mood should lift very quickly, so long as you don’t consume any more of the particular item. (See the ‘Food and mood’ pages on the Mind website.)

Street drugs and alcohol

Although you may be very tempted to have a drink to cheer you up, alcohol is a depressant, and will tend to make you feel worse overall. Some street drugs can also make you depressed, especially if used repeatedly. (For more information, see Understanding the mental health effects of street drugs.)


Although no specific genes for depression have been identified, it does seem to run in families to some extent, and some of us are more prone to depression than others. This could also be because we learn behaviour and ways of responding from our relatives, as well as inheriting our genes from them.

Chemical changes in the brain

Because antidepressants work by changing brain chemistry, many people have assumed that depression must be caused by changes in brain chemistry that 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, apart from the effects of medication, 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. Although there are physical tests which are occasionally used in research on depression, they are not very accurate or consistent, and there are none that are done routinely to help make a diagnosis.


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