Causes of Depression - Further Reading

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The causes of depression are numerous and complex…

They can be organised in to:

  • biological causes

  • life events 

  • cognitive style (how you view yourself and your place in the world, determined in early life)

In other words, they can be organised in to: 

  • biological

  • social 

  • psychological

These causes are not mutually exclusive. They interact. More than one cause is often present in the same person. The nature-nurture debate is defunct. Depression is usually caused by both. Let us start with the biological causes, which make us more vulnerable to depression:



Keeping life stresses constant, some people are more vulnerable than others. There’s a bell curve of vulnerability. Most of us fall in the middle of the curve – requiring a moderate amount of stress to get depressed. The rest fall at the tail ends (those who are very sensitive and need very little stress to trigger an episode, and those who are stoical to an extreme degree). The genetics of depression is complex. Although having a first degree family member increases your vulnerability roughly threefold, this will be mediated by a lot of genes of small effect, and environment will play a large part. There will be come genes that act indirectly to increase vulnerability to depression, by affecting your temperament. For example, some babies some to be born with more neuroticism and childhood fears than others. Neuroticism increases our vulnerability to depression, but depression is far from guaranteed. Stress combines with neuroticism to manifest psychiatric disorder. This is called the “stress-liability model”, and it makes sense. Research in the area is complicated, however, because the order of effect can be unclear.  For example, neurotic people might bring more stress on themselves because of the life choices they make. 

Drugs and alcohol

People withdrawing from stimulant drugs like crystal meth, cocaine and MDMA sometimes become depressed enough to harm themselves. LSD can cause permanent psychosis and secondary depression due to being plagued by unpleasant flashbacks. Alcohol reduces anxiety in the short term but increases it in the long term, and causes adverse changes in the pleasure chemical dopamine in the brain.


Certain medications cause depression in unpredictable and unknown ways. These include interferon-alpha (used to treat viral hepatitis), steroids, some oral contraceptives, some antihypertensive drugs, and roaccutane for acne. However, they will not cause depression in everyone. Determining who is vulnerable is difficult but if you had depression before then that increases the risk.

Physical illnesses that cause depression include:

  • Infections – flu, HIV, mono (Glandular Fever)

  • Hormonal problems – thyroid, parathyroid, adrenal gland problems

  • Brain disorders – multiple sclerosis, brain trauma, tumours

  • Inflammation – lupus, rheumatoid arthritis (due to a direct effect of inflammation on the brain). 

  • Painful and disabling conditions – including arthritis, sciatica, stroke, some cancers. 

Life Events (Social)

Some life events are more likely to trigger depression than others. These include:

  • Divorce

  • Redundancy

  • Imprisonment

  • Bereavement

  • Moving home

But their predictive value at the level of the individual is poor. I know lots of people who have been through these experiences and not suffered depression. It’s not that simple. 

The meaning of events is as important as the events themselves. I will come back to this when we talk about cognitive style

Another important consideration is the consequence of the event. Consequences can have a much more severe and long lasting impact than the event itself. 

Consider divorce. You would be inhuman if you did not have some short term grief reaction, but you can see how this might deepen to a depression if the consequences were acrimony, a court case over money and a protracted tussle over accommodation of the children. What if the split caused you to lose your job, or your most important friends? Redundancy might cause depression in someone with few future choices, but if you were on “gardening leave” while you set up your own business, for example, or you had a better job to go to , then the impact on your mental health might actually be very different. Chronic unemployment is a much bigger risk factor for depression than a brief period of unemployment.

Consequences that are most likely to lead to depression include:

  • loss of status

  • loss of emotional support

  • humiliation

and arguably the most important:

  • entrapment in a stressful situation (custody battle, poverty, homelessness, debt)

Entrapment is like Seligman’s cage that won’t let the dog escape from a shock, causing it to adopt a state of “learned helplessness”. It is chronic stress that causes the slowing down of mental and physical activity in depression, not a one off event.

For the same reason, a seemingly innocuous event can be the final straw to tip you in to depression if occurs on background of persistent life difficulties, like debt or marital strife.

Consider that ongoing relationship problems – conflict, degradation, abuse, manipulation – are very ‘depressogenic’.

Cognitive style (Psychological)

Early life event research just focused on the impact of events per se on our emotional and physical health, by examining medical records for evidence of the relative number of people impacted by them. However, just because more people become depressed following a divorce than following a house move does not mean that you will react in this way. Everyone reacts to events in different ways. Not everyone grieves in the same way after the death of a loved one, for example. Their own coping skills and temperament are important, as well as the relationship with the deceased. It seems obvious when you look at this way: the meaning of events is as important as the events themselves. 

The way that we attach meaning to events is built around our experiences in early life. These experiences create the prism through which we view the world. This prism can be quite distorted and give us a false view of things. Cognitive therapists call this prism the “schema” – the system of beliefs and assumptions that were born out of experience, determine how we perceive events, and the conclusions we make about the world and ourselves.

Sadness and Bullying

Imagine if you felt terrible sadness when your father left home as a child. Would that make you more prone to depression if your husband were to leave you later in life? What about if you had a parent who constantly criticised you, would you react differently to criticism from your boss? If you were bullied at school would this effect how you responded to bullying at work? Perhaps bullying made you strive very hard for success, to undo all that early criticism and prove to those detractors that you are much better than them. Such striving can lead to exhaustion and depression.

Childhood maltreatment

Childhood maltreatment is an important vulnerability factor for depression. The main types of abuse are physical, sexual, emotional and neglect. People often forget about the terrible effects of emotional abuse – humiliating and critical comments, for example – which lead to low self-esteem and poor choices in relationships later on. 


Neglect or inconsistent care can lead to insecurity and lack of trust, whereas physical abuse can lead to complex post-traumatic stress disorder (sensitivity to noise, high levels of anxiety, nightmares, flashbacks of abuse). 

In summary, childhood maltreatment can lead to a number of cognitive styles and behaviours that might make us more prone to depression in adult life:

  • A glass half empty view of the world (bad things will always happen to me)

  • Low self esteem (I am not worthy of love).

  • Perfectionism (I must strive for perfection to prove that I’m not worthless).

  • Narcissism (craving attention and being sensitive to criticism because of unacknowledged self-loathing)

  • Fear of abandonment by partners and friends

  • Trust issues and testing loyalty

  • High levels of vigilance and anxiety around thinking that people present a threat when they don’t.

  • Promiscuity and seeking out sexually abusive partners.

  • Choosing partners that are critical and shaming because you think that is normal, or tolerating domestic violence.

Psychotic disorders like paranoid schizophrenia

Sometimes people who are psychotic (who experience hallucinations and delusions) can become depressed if they go for long periods without being treated. This makes sense if you think about it. This is just another source of chronic stress. Imagine thinking that your life is in danger from imaginary enemies for days or weeks on end. 

Resilience – a quick word

You can not talk about how stress causes depression without considering the antidote to stress - resilience. Psychological resilience is built in childhood by a loving and nurturing environment. Later in life, social support enhances our resilience. We are social mammals. To be truly happy we need to feel loved and cared for. Practical support is important but emotional support is the most powerful antidote to stressful life events and chronic life difficulties. 

George TaylorComment