Neuroscientists still don’t fully understand what happens in the brain when we become depressed or exactly what causes depression. Perhaps you’ve already suspected that depression is more complex than most disorders and that many different risk factors interact to create the low mood, the lack of interest in activities and other ingredients that make life meaningful?

This article aims to give you as much information as possible about the causes of depression, so that you can better understand this mysterious disorder and hopefully use your knowledge to prevent it.

We’ll begin by diving deep into the brain in the hope of finding the latest theories about what happens in our heads when depressed. If you’re more interested in why depression happens – the behavioural and environmental factors – skip ahead to the section called 11 more causes of depression.

More than a chemical imbalance

For many years, researchers believed that the root cause of depression was a chemical imbalance in the brain. Depression was thought to occur because the brain didn’t produce enough of certain chemicals (or neurotransmitters), such as dopamine, serotonin and norepinephrine, which are important for mood regulation.

That’s why depression is treated with antidepressants. Some antidepressants help the brain produce more of the neurotransmitters and others help these chemicals hang around a little longer inside your head. 

Nowadays, the story is different. 

Even though antidepressants immediately provide the brain with more neurotransmitters, it takes several weeks for the medications to work. This is a fact that has made more than one researcher scratch their heads. If the chemical imbalance is the problem, why doesn’t depression disappear as soon as we fix the chemical imbalance?

Well, new research suggests that depression is more complicated than that. 

Today, researchers believe that a more probable cause of depression is a slow production of new brain cells and poor connections between brain cells, especially in the prefrontal cortex (PFC) and in the hippocampus. Among other things, these brain areas are responsible for mood regulation and information processing.

brain parts

So, it’s not the lack of dopamine, serotonin and norepinephrine that causes depression. In fact, neuroscientist Dr Moncrieff and colleagues have once and for all concluded that there is no significant connection between low serotonin levels and depression.

And according to Harvard Health Publishing, there is some evidence showing that antidepressants do spur the growth of new brain cells in the hippocampus. This process takes a few weeks, which could explain why antidepressants don’t have an immediate effect on depression. 

So, the real value of antidepressants may be that they help brain cells grow, not that they fix a chemical imbalance in the brain. If this is true, future antidepressants should be specifically designed to promote brain cell growth.

Less invasive (but equally effective) depression treatments include:

  • Physical exercise (which is associated with hippocampal growth).
  • tDCS (which helps the brain cells in the prefrontal cortex to activate and build stronger connections).
  • Mindfulness meditation (which improves connections in the prefrontal cortex and the hippocampus).

Read more about antidepressants here: What are the side effects of antidepressants? – Learn about side effects, tolerance and withdrawal and here Do antidepressants work?

baby braincell

11 more causes of depression

Now you know more about what happens in your brain when depressed, but why does it happen? Why do connections between brain cells become damaged? 

Well, there is no simple answer to this question. Sorry. As it turns out, the human brain is a frustratingly complex thing, and usually, more than one factor is involved in depression.

However, there are several known risk factors for developing depression and the following sections include some of the most important ones.

1. Genes as a cause of depression. Depression is, to some extent, hereditary. This means that if you have a close relative, such as a parent or sibling, who has experienced depression, you are at higher risk of developing the disorder yourself. However, not all cases of depression include a genetic component and you’re not destined to develop depression only because your relatives have it. Usually, genes and environment interact in a way that triggers depression.

Even though depression runs in the family, it may be triggered by stressful life events.

depression DNA

2. Stressful life events as causes of depression. Difficult life experiences, such as separations, conflicts, betrayal, bereavement and losses can trigger depression. When more than one of these stressful events take place within a short period of time, the risk of developing depression increases. It can be extremely important to seek support and open up to your friends when you’re going through something difficult. People who disconnect from family and friends after stressful experiences are at higher risk of developing depression.

Other stressful situations which increase the risk of depression are:

  • An experience of loss of control at work, for example not being able to change or influence your job situation. 
  • Feelings of loneliness and being cut off from your family and friends. 
  • Financial difficulties.
  • Big changes in life can sometimes trigger depression, even events that we generally think of as positive, such as moving to a new city, getting married or starting a family.

3. Early losses and trauma as causes of depression. Early losses, such as the loss of a parent, or trauma, such as childhood abuse, increase the risk of developing depression as an adult. If you’ve had any of these difficult experiences as a child and you’re currently going through a stressful time, be sure to seek support from friends, family or a professional.

4. Giving birth as a cause of depression. Postpartum depression is a form of depression that occurs in connection with having a child. Approximately 15% of people giving birth experience depression as a consequence.
Read more about: What is postpartum depression (PPD)? – more than just the baby blues.

postpartum depression

5. Seasonal changes as causes of depression. Seasonal depression or Seasonal Affective Disorder (SAD) is a type of depression triggered by seasonal changes. Typically, this type of depression returns every fall/winter and lifts during spring when there is more natural sunlight. Some people experience a less common type of seasonal depression where the symptoms occur during spring and summer.

6. Lack of movement as a cause of depression. Regular exercise works as depression treatment, while a sedentary lifestyle increases the risk of depression. 30-40 minutes of exercise 3-4 times a week is as effective as taking antidepressants or engaging in psychotherapy. Taking a sweaty walk (preferably in nature) lifts your mood and improves concentration immediately.
Read more about exercise and depression here: All you need to know about exercise and depression – How to build a treatment routine that lasts

7. Poor diet as a cause of depression. A diet with lots of fruit, fish, olive oil and vegetables can decrease depressive symptoms, while a poor diet increases the risk of depression. People who eat a lot of red meat, added sugars, high-fat dairy products, fried foods and creamy sauces experience more depressive symptoms and depressed moods than others. In the past, researchers thought that a depressed mood made people eat more junk food. Today, we know that the opposite is also true. Eating too much fat, white flour, sugar and processed meat increases inflammation in the body and the risk of depression. 

Read more about diet and depression here: An easily digested guide to diet and depression – How to eat your way out of depression.

western diet

8. Poor sleep quality as a cause of depression. Depression often leads to sleep disturbance and 90% of depressed people experience sleeping problems. Simultaneously, poor quality sleep intensifies the symptoms of depression and increases the risk of becoming depressed. Perhaps you’ve noticed that sleeping poorly makes it difficult to concentrate and manage strong emotions? Improving your sleeping habits can break this vicious cycle and reduce your symptoms.
Read more here: All you need to know about depression and sleep – The most effective sleep strategies for improving depression

9. Alcohol as a cause of depression. People who frequently drink alcohol are at higher risk of developing depression and depression increases the risk of alcohol abuse. As you can imagine, alcohol and depression in combination is fertile soil for a vicious cycle. 

Alcohol can serve as a form of ‘self-medication’ for people with depression. It can be tempting to drink something that will temporarily reduce your level of anxiety and trick your brain into becoming more carefree. In the long run, however, alcohol misuse will worsen depressive symptoms and anxiety, which may tempt you to drink even more.  

Be careful not to drink too much when going through depression, especially not late at night as it will affect your sleep quality. 

So, how much alcohol is too much? Well, because alcohol is an addictive substance, all forms of drinking it involves a health risk. According to the NHS, drinking more than 14 units of alcohol a week is considered high-risk drinking and less than 14 units is low-risk (there is no ‘safe’ amount of alcohol). 14 units is equivalent to 6 pints of average-strength beer or 10 small glasses of low-strength wine. In Sweden, women are recommended not to drink more than 9 units and never more than 3 units on the same day. Men are recommended not to drink more than 14 units and never more than 4 units on the same day. 

These are signs of alcohol use disorder (when drinking too much):

  • Drinking frequently or daily
  • Drinking more than 3-4 units in any one episode
  • Craving alcohol
  • Hiding alcohol so others won’t observe how much you consume
  • Continuing to drink despite negative consequences, for example to physical health or personal relationships
  • Avoiding activities to drink
  • Continued drinking despite symptoms of depression or anxiety

10. Smoking as a cause of depression. According to the NHS, stopping smoking can have the same beneficial effects on depressive symptoms as antidepressants. After giving up their cigarettes, people with mental health problems report feeling much calmer, more positive and having an increased quality of life. It’s also true that smokers are more likely than non-smokers to develop depression.

So, if smoking leads to depression and stress, why do smokers feel more relaxed when smoking? 

It’s a common misunderstanding that smoking relieves anxiety and stress. The truth is that cigarettes most likely caused the stress in the first place. 

Smoking is addictive and addictive substances create withdrawal symptoms, or cravings. When smokers haven’t had a cigarette in a while, they start feeling restless and anxious (common symptoms of withdrawal) and they crave another cigarette for relief. So, when they light up, the craving disappears momentarily and the smokers associate the improved mood with the cigarette (and the absence of cigarettes with irritability and stress). 

When people stop smoking, they don’t have to deal with the cravings anymore and their anxiety, depression and stress levels drop.

stop cigarette

11. Medical problems as causes of depression. Some physical illnesses bring with them an increased risk of depression.

  • Having coronary heart disease, cancer or other longstanding and life-threatening medical conditions places a person under extreme stress and involves an increased risk of depression
  • Hypothyroidism (having an underactive thyroid) is a condition where the thyroid gland doesn’t produce enough of certain hormones. It can cause depression-like symptoms, for example, extreme fatigue, weight gain and a lack of interest in sex. Over time, these symptoms can develop into depression.
  • Some forms of severe head injuries can trigger mood swings and other mood-related problems, such as depression.

In conclusion

Depression is a somewhat mysterious and complex disease and experts still don’t know exactly what happens in the brain when we become depressed. However, there are many known risk factors for developing depression, such as:

  1. Genes
  2. Stressful life events
  3. Early losses and trauma
  4. Childbirth
  5. Seasonal changes 
  6. Lack of exercise
  7. Poor diet
  8. Poor sleep quality
  9. Alcohol
  10. Smoking
  11. Medical problems

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