This claim is very widespread, but I haven't seen it in any sources I'd consider trustworthy.

  • I think this is an excellent candidate for the new biology site. I’ll flag to move. Jan 3, 2012 at 15:52
  • Did you do any research at all? Like a Google search? Jan 3, 2012 at 17:34
  • @DJClayworth Yes - admittedly I didn't pick the best terms this time, but they didn't include "affect". These aren't very impressive results.
    – RomanSt
    Jan 3, 2012 at 22:59
  • The search "stress weakens immune system" yields a paper by the American Psychological Association as its second hit. Jan 4, 2012 at 20:28

1 Answer 1


Yes, stress reduces the immune function.

There are numerous peer-reviewed papers on the subject:

Reduction of immune function in life stress and depression

Reduced cell-mediated immune function has been found in depressed patients and in distressed persons undergoing threatening life events.

Stress, emotion, and human immune function.

Chronic stress has been associated with suppression of immune function, and there is evidence that the immune system may not adapt over time. Effects of stress accompanying social disruption and psychological depression, when demonstrated, have been consistently adverse.

Psychoneuroimmunology: Psychological influences on immune function and health.

This review focuses on human psychoneuroimmunology studies published in the past decade. Issues discussed include the routes through which psychological factors influence immune function, how a stressor's duration may influence the changes observed, individual difference variables, the ability of interventions to modulate immune function, and the health consequences of psychosocially mediated immune dysregulation.

Psychoneuroimmunology is actually a fully fledged field of study:

Psychoneuroimmunology (PNI) is the study of the interaction between psychological processes and the nervous and immune systems of the human body.

  • They seem to imply the unpleasant kind of stress in these studies. Do you know whether things like working on a particularly fun project for months non-stop has the same kinds of negative consequences for the immune system?
    – RomanSt
    Jan 3, 2012 at 23:07
  • Different things can be stressful for different people. There is no way to tell if someone is going to be stressed by that. Jan 4, 2012 at 20:30
  • 1
    @romkyns stress in a physiological sense is not just adrenaline feuled fear or anger, it could be sleep deprivation or starving yourself. Exercise is also a stressor, and can be bad for you in large amounts. So if by fun you mean putting your body through lots of stress then it will have negative consequences! I would recommend "Why zebras don't get ulcers" by Robert Sapolsky, who is an expert on stress if you want to learn more :)
    – Tjaart
    Oct 9, 2012 at 7:23

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