Lewis Wolpert: 'The immune system can have profound effects on thinking and emotion'

I had persuaded myself that depression was related to abnormal sadness, hence my book, Malignant Sadness. But I now realise that I might have missed a very important aspect of depression, its relationship to the immune system. Friends did try to persuade me to take it seriously, but to no avail. Then I read an article in a leading medical journal that described the treatment of hepatitis with alpha interferon. I was struck by the fact that they gave such patients an antidepressant at the same time, for otherwise there was a high incidence of depression. I contacted the authors in the USA and they told me that their patients' depression was not related to sadness, but more to fatigue. They also sent me a review which has persuaded me how important the immune system may be in depression.

That there is a relationship between physical and psychological health goes back to the ancient Greeks, but it is only quite recently that it has been recognised that the immune system can have profound effects on thinking and emotion. One link is via stress. The stress response is adaptive in many situations, such as danger, and helps the individual to deal with the threat. The physiological response involves both hormones and the nervous system, and makes more energy available. However, this becomes a danger to health when it remains chronically overactive, and this condition is frequently found in patients with severe depression.

Stress and depression can affect the immune system, which is complex, with many interactions between cells such as lymphocytes and macrophages, those white cells that are at the core of the immune system, and numerous cytokines, the chemical signals between these and other cells. Chronic stress can affect the function of lymphocytes and cytokine production, and a longer time is needed to recover from an infectious disease. Surprisingly, the same stressors can also activate the immune system.

There is now evidence that depression can both activate and suppress immune-system function. With immune-system activation, there can be induction of a state that is called sickness behaviour, which resembles depression. It is this that underlies the depression caused by giving interferon, which is itself a cytokine controlling aspects of the immune system. The similarity of depression with sickness behaviour predicts that those with illnesses should have higher rates of depression. This is the case.

Increased cytokine levels after birth could account for postnatal depression. How the cytokines act on the brain to cause depression is not clear, but they can enter the brain. Stress hormones such as cortisol are very likely key players, as depression in many is associated with an increase in the activity of the interactions between the hypothalamus, pituitary and adrenal glands, which are activated by stress. Increase in cytokines can stimulate this system, and the normal negative feedback that returns it after a short while to normal function may be prevented from operating.

There is a further fascinating connection with the placebo effect. In his new book, Placebo, Dylan Evans argues that the acute phase response is involved. This response is a result of some injury and the immune system is activated, moreover only those illnesses that involve this response are capable of being relieved by the placebo effect, and they include depression. The complexity of all these interacting factors is disturbing, but will eventually lead to new drugs for depression, perhaps acting on the immune system.

Lewis Wolpert is Professor of Biology as Applied to Medicine at UCL

Start your day with The Independent, sign up for daily news emails
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: Practice Accountant - Bournemouth - £38,000

£32000 - £38000 per annum: Ashdown Group: A successful accountancy practice in...

SThree: Trainee Recruitment Consultant

£18000 - £23000 per annum + Uncapped commission: SThree: Does earning a 6 figu...

Recruitment Genius: SEO Executive

£18000 - £25000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: New Lift Sales Executive - Lift and Elevators

£35000 - £40000 per annum: Recruitment Genius: A challenging opportunity for a...

Day In a Page

The saffron censorship that governs India: Why national pride and religious sentiment trump freedom of expression

The saffron censorship that governs India

Zareer Masani reveals why national pride and religious sentiment trump freedom of expression
Prince Charles' 'black spider' letters to be published 'within weeks'

Prince Charles' 'black spider' letters to be published 'within weeks'

Supreme Court rules Dominic Grieve's ministerial veto was invalid
Distressed Zayn Malik fans are cutting themselves - how did fandom get so dark?

How did fandom get so dark?

Grief over Zayn Malik's exit from One Direction seemed amusing until stories of mass 'cutting' emerged. Experts tell Gillian Orr the distress is real, and the girls need support
The galaxy collisions that shed light on unseen parallel Universe

The cosmic collisions that have shed light on unseen parallel Universe

Dark matter study gives scientists insight into mystery of space
The Swedes are adding a gender-neutral pronoun to their dictionary

Swedes introduce gender-neutral pronoun

Why, asks Simon Usborne, must English still struggle awkwardly with the likes of 's/he' and 'they'?
Disney's mega money-making formula: 'Human' remakes of cartoon classics are part of a lucrative, long-term creative plan

Disney's mega money-making formula

'Human' remakes of cartoon classics are part of a lucrative, long-term creative plan
Lobster has gone mainstream with supermarket bargains for £10 or less - but is it any good?

Lobster has gone mainstream

Anthea Gerrie, raised on meaty specimens from the waters around Maine, reveals how to cook up an affordable feast
Easter 2015: 14 best decorations

14 best Easter decorations

Get into the Easter spirit with our pick of accessories, ornaments and tableware
Paul Scholes column: Gareth Bale would be a perfect fit at Manchester United and could turn them into serious title contenders next season

Paul Scholes column

Gareth Bale would be a perfect fit at Manchester United and could turn them into serious title contenders next season
Inside the Kansas greenhouses where Monsanto is 'playing God' with the future of the planet

The future of GM

The greenhouses where Monsanto 'plays God' with the future of the planet
Britain's mild winters could be numbered: why global warming is leaving UK chillier

Britain's mild winters could be numbered

Gulf Stream is slowing down faster than ever, scientists say
Government gives £250,000 to Independent appeal

Government gives £250,000 to Independent appeal

Donation brings total raised by Homeless Veterans campaign to at least £1.25m
Oh dear, the most borrowed book at Bank of England library doesn't inspire confidence

The most borrowed book at Bank of England library? Oh dear

The book's fifth edition is used for Edexcel exams
Cowslips vs honeysuckle: The hunt for the UK’s favourite wildflower

Cowslips vs honeysuckle

It's the hunt for UK’s favourite wildflower
Child abuse scandal: Did a botched blackmail attempt by South African intelligence help Cyril Smith escape justice?

Did a botched blackmail attempt help Cyril Smith escape justice?

A fresh twist reveals the Liberal MP was targeted by the notorious South African intelligence agency Boss