<p>Short answer: The effect of stress and trauma on IQ varies significantly according to type and severity, but is overall fairly low relative to normal variation in scores.</p>
<p>IQ test development is heavily concerned with <a href="https://en.wikipedia.org/wiki/Reliability_(statistics)" rel="nofollow noreferrer">reliability</a> (consistent scores) so while some variation is inevitable, <a href="https://en.wikipedia.org/wiki/Intelligence_quotient#Reliability" rel="nofollow noreferrer">IQ tests</a> are designed to minimize the impact of stress:</p>
<blockquote>
<p>... test-takers may have varying scores when taking the same test on
differing occasions, and may have varying scores when taking different
IQ tests at the same age. ... For modern tests, the confidence interval
can be approximately 10 points ...</p>
</blockquote>
<p>Additionally, particularly low or high IQ scores are less reliable than median scores.  Nonetheless:</p>
<blockquote>
<p>Outside influences such as low motivation or high anxiety can
occasionally lower a person's IQ test score.</p>
</blockquote>
<p>So, up to approximately 10 IQ points difference in scores can be accounted for by measurement error and performance variability, but stressors can potentially result in larger differences.</p>
<p>Despite the broad scope of the question, I was not able to find any recent dedicated literature reviews on the effects of any particular type of stress or trauma on IQ, so conclusions are based on a sample of recent available studies.</p>
<p><a href="https://doi.org/10.4172/2375-4494.1000107" rel="nofollow noreferrer">Marcus Jenkins et al (2013)</a> looked at the effects of family stress on child IQ:</p>
<blockquote>
<p>... we identified four subconstructs that capture family stress:
Marital conflict, parenting stress, depressive symptoms and maternal
history of psychiatric disorders. ... None of the family stress
components mediated the effect of the SES components on child IQ.</p>
</blockquote>
<p><a href="https://doi.org/10.1001/archpedi.156.3.280" rel="nofollow noreferrer">Delaney-Black et al (2002)</a>, <a href="https://doi.org/10.1353/mpq.2006.0017" rel="nofollow noreferrer">Ratner et al (2006)</a>, <a href="https://doi.org/10.1017/S0954579403000166" rel="nofollow noreferrer">Koenen et al (2003)</a>, <a href="https://doi.org/10.1007/s10896-006-9054-y" rel="nofollow noreferrer">Ybarra, Wilkens, &amp; Lieberman (2007)</a>, and <a href="https://doi.org/10.1186/1471-2458-12-562" rel="nofollow noreferrer">Ghazi et al (2012)</a> looked at the effects of violence and trauma on child IQ:</p>
<blockquote>
<p>... a child experiencing both violence exposure and trauma-related
distress at or above the 90th percentile would be expected to have a
7.5-point (SD, 0.5) decrement in IQ ...</p>
</blockquote>
<p><a href="https://doi.org/10.1002/hbm.23988" rel="nofollow noreferrer">Butler et al (2018)</a> and <a href="https://doi.org/10.1073/pnas.1000690107" rel="nofollow noreferrer">Sharkey (2010)</a> found similar effects on adolescent IQ.  However, <a href="https://dx.doi.org/10.1037%2F0021-843X.115.2.332" rel="nofollow noreferrer">Saigh et al (2006)</a> and <a href="https://doi.org/10.1016/j.chiabu.2008.08.002" rel="nofollow noreferrer">DePrince, Weinzierl, &amp; Combs (2009)</a> also looked at the impact of violence and trauma on child IQ, but found no effect.</p>
<p><a href="https://doi.org/10.1002/pits.21809" rel="nofollow noreferrer">Viezel, Freer, &amp; Castillo (2015)</a> looked at the effect of abuse and neglect, and found an approximately 5-point decrement in child IQ, while <a href="https://doi.org/10.1007/s10826-008-9212-3" rel="nofollow noreferrer">Doerfler, Toscano, &amp; Connor (2008)</a> looked at the effect of abuse on adolescent IQ:</p>
<blockquote>
<p>For Performance IQ or Full Scale IQ scores, there were no significant
main effects for gender or abuse experience.</p>
</blockquote>
<p><a href="https://doi.org/10.1080/19361521.2012.633239" rel="nofollow noreferrer">Kira et al (2012)</a>, <a href="https://doi.org/10.1037/a0022121" rel="nofollow noreferrer">Kira et al (2012)</a>, and <a href="https://doi.org/10.1080/10926771.2014.904463" rel="nofollow noreferrer">Kira et al (2014)</a> looked at the effect of a variety of different stressors and traumas - including abuse, bullying, abandonment, and violence - on adolescent IQ in 2 vulnerable sub-groups:</p>
<blockquote>
<p>Our findings support the hypothesis that different trauma types have
different influences, some positive and some negative. ... In
conclusion, trauma type differentially impacts IQ.</p>
</blockquote>
<p>However, the effect of stress on overall IQ was small (r&lt;0.15).</p>
<p>Note that many studies found significant effects of stress and trauma on IQ sub-tests and sub-components, though overall IQ was often not significantly affected.  Note also that ethical conduct makes stress and trauma difficult to manipulate experimentally, so these studies are largely <a href="https://en.wikipedia.org/wiki/Retrospective_cohort_study" rel="nofollow noreferrer">retrospective</a>, or at best <a href="https://en.wikipedia.org/wiki/Prospective_cohort_study" rel="nofollow noreferrer">prospective</a>, but not <a href="https://en.wikipedia.org/wiki/Randomized_controlled_trial" rel="nofollow noreferrer">randomized controlled</a> studies.  Thus, study quality is an issue, making conclusions tentative - in particular, the direction of causality is not always entirely clear.</p>

CC BY-SA 4.0
2021-04-01T07:09:41.837Z
2023-04-25T19:45:05.677Z
2023-04-25T19:45:05.677Z
Arnon Weinberg
<p>Stress will certainly affect your test performance and cognition, see <a href="https://d1wqtxts1xzle7.cloudfront.net/42357220/The_effects_of_stress_and_stress_hormone20160207-17857-1oizaoo.pdf?1454910197=&amp;response-content-disposition=inline%3B%20filename%3DThe_effects_of_stress_and_stress_hormone.pdf&amp;Expires=1616848349&amp;Signature=MhxGouNkwHD%7EQHynLyxMrkunLzSag879vUJfDfr-W0BrLWukLW8JjoNNM%7EvuCJtl69B4Xp%7EPFhCuWFo87t6R9fPeWoeKKSSruHQKxkNpzvJszVgwQOoJ6B40cbMMfQReEVQIy1-hgmQxU2DjM8htuCPGTfR25diZDJiB4fW3tfvA9rO-hD4PEtcY5ObVRiLpzmy7OKwIByAIfXSVgT5kPhKcEc2%7E4ycqv7eSSsrajgSEPg-ztkQi1%7E0n4vCoMbITvx9e1GiBmqIQYd0fVP2ZDK5ddAM1Dz0TkuJ0unIGxtZ8DPunN-qdqxqTgGeYmG3aSKpT7EhuYrjhm153A4ZD1g__&amp;Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA" rel="nofollow noreferrer">Lupien 2007</a>.</p>
<p>It might be a bit hard to measure this in an experiment, as the same individuals have to take the test with and without stress. But then you have to control for some learned effect, second time the test might be easier.</p>

CC BY-SA 4.0
2021-03-27T11:37:48.560Z
2021-03-27T11:37:48.560Z
Dirk N
<p>Does <a href="https://en.wikipedia.org/wiki/Psychological_stress" rel="nofollow noreferrer">mental stress</a> or <a href="https://en.wikipedia.org/wiki/Psychological_trauma" rel="nofollow noreferrer">trauma</a> have a significant impact on IQ test performance relative to baseline, and if so, how much?</p>
<p>For example, if a person is affected by abuse, bullying, neglect, or some other stressor or trauma, then how much of an effect would that have on their test score?</p>

<measurement><intelligence><iq><stress><trauma>
How are IQ test scores affected by psychological stress or trauma?
user2638180
# How are IQ test scores affected by psychological stress or trauma?

(Asked by: username_0 on 2021-03-23)

Does [mental stress](https://en.wikipedia.org/wiki/Psychological_stress) or [trauma](https://en.wikipedia.org/wiki/Psychological_trauma) have a significant impact on IQ test performance relative to baseline, and if so, how much?

For example, if a person is affected by abuse, bullying, neglect, or some other stressor or trauma, then how much of an effect would that have on their test score?

**Tags:** measurement, intelligence, iq, stress, trauma


---

## 2 answers

### Answer by username_1 on 2021-04-01. Score: 3

Short answer: The effect of stress and trauma on IQ varies significantly according to type and severity, but is overall fairly low relative to normal variation in scores.

IQ test development is heavily concerned with [reliability](https://en.wikipedia.org/wiki/Reliability_(statistics)) (consistent scores) so while some variation is inevitable, [IQ tests](https://en.wikipedia.org/wiki/Intelligence_quotient#Reliability) are designed to minimize the impact of stress:

> ... test-takers may have varying scores when taking the same test on
> differing occasions, and may have varying scores when taking different
> IQ tests at the same age. ... For modern tests, the confidence interval
> can be approximately 10 points ...

Additionally, particularly low or high IQ scores are less reliable than median scores. Nonetheless:

> Outside influences such as low motivation or high anxiety can
> occasionally lower a person's IQ test score.

So, up to approximately 10 IQ points difference in scores can be accounted for by measurement error and performance variability, but stressors can potentially result in larger differences.

Despite the broad scope of the question, I was not able to find any recent dedicated literature reviews on the effects of any particular type of stress or trauma on IQ, so conclusions are based on a sample of recent available studies.

[Marcus Jenkins et al (2013)](https://doi.org/10.4172/2375-4494.1000107) looked at the effects of family stress on child IQ:

> ... we identified four subconstructs that capture family stress:
> Marital conflict, parenting stress, depressive symptoms and maternal
> history of psychiatric disorders. ... None of the family stress
> components mediated the effect of the SES components on child IQ.

[Delaney-Black et al (2002)](https://doi.org/10.1001/archpedi.156.3.280), [Ratner et al (2006)](https://doi.org/10.1353/mpq.2006.0017), [Koenen et al (2003)](https://doi.org/10.1017/S0954579403000166), [Ybarra, Wilkens, & Lieberman (2007)](https://doi.org/10.1007/s10896-006-9054-y), and [Ghazi et al (2012)](https://doi.org/10.1186/1471-2458-12-562) looked at the effects of violence and trauma on child IQ:

> ... a child experiencing both violence exposure and trauma-related
> distress at or above the 90th percentile would be expected to have a
> 7.5-point (SD, 0.5) decrement in IQ ...

[Butler et al (2018)](https://doi.org/10.1002/hbm.23988) and [Sharkey (2010)](https://doi.org/10.1073/pnas.1000690107) found similar effects on adolescent IQ. However, [Saigh et al (2006)](https://dx.doi.org/10.1037%2F0021-843X.115.2.332) and [DePrince, Weinzierl, & Combs (2009)](https://doi.org/10.1016/j.chiabu.2008.08.002) also looked at the impact of violence and trauma on child IQ, but found no effect.

[Viezel, Freer, & Castillo (2015)](https://doi.org/10.1002/pits.21809) looked at the effect of abuse and neglect, and found an approximately 5-point decrement in child IQ, while [Doerfler, Toscano, & Connor (2008)](https://doi.org/10.1007/s10826-008-9212-3) looked at the effect of abuse on adolescent IQ:

> For Performance IQ or Full Scale IQ scores, there were no significant
> main effects for gender or abuse experience.

[Kira et al (2012)](https://doi.org/10.1080/19361521.2012.633239), [Kira et al (2012)](https://doi.org/10.1037/a0022121), and [Kira et al (2014)](https://doi.org/10.1080/10926771.2014.904463) looked at the effect of a variety of different stressors and traumas - including abuse, bullying, abandonment, and violence - on adolescent IQ in 2 vulnerable sub-groups:

> Our findings support the hypothesis that different trauma types have
> different influences, some positive and some negative. ... In
> conclusion, trauma type differentially impacts IQ.

However, the effect of stress on overall IQ was small (r<0.15).

Note that many studies found significant effects of stress and trauma on IQ sub-tests and sub-components, though overall IQ was often not significantly affected. Note also that ethical conduct makes stress and trauma difficult to manipulate experimentally, so these studies are largely [retrospective](https://en.wikipedia.org/wiki/Retrospective_cohort_study), or at best [prospective](https://en.wikipedia.org/wiki/Prospective_cohort_study), but not [randomized controlled](https://en.wikipedia.org/wiki/Randomized_controlled_trial) studies. Thus, study quality is an issue, making conclusions tentative - in particular, the direction of causality is not always entirely clear.


---

### Answer by username_2 on 2021-03-27. Score: 0

Stress will certainly affect your test performance and cognition, see [Lupien 2007](https://d1wqtxts1xzle7.cloudfront.net/42357220/The_effects_of_stress_and_stress_hormone20160207-17857-1oizaoo.pdf?1454910197=&response-content-disposition=inline%3B%20filename%3DThe_effects_of_stress_and_stress_hormone.pdf&Expires=1616848349&Signature=MhxGouNkwHD%7EQHynLyxMrkunLzSag879vUJfDfr-W0BrLWukLW8JjoNNM%7EvuCJtl69B4Xp%7EPFhCuWFo87t6R9fPeWoeKKSSruHQKxkNpzvJszVgwQOoJ6B40cbMMfQReEVQIy1-hgmQxU2DjM8htuCPGTfR25diZDJiB4fW3tfvA9rO-hD4PEtcY5ObVRiLpzmy7OKwIByAIfXSVgT5kPhKcEc2%7E4ycqv7eSSsrajgSEPg-ztkQi1%7E0n4vCoMbITvx9e1GiBmqIQYd0fVP2ZDK5ddAM1Dz0TkuJ0unIGxtZ8DPunN-qdqxqTgGeYmG3aSKpT7EhuYrjhm153A4ZD1g__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA).

It might be a bit hard to measure this in an experiment, as the same individuals have to take the test with and without stress. But then you have to control for some learned effect, second time the test might be easier.


---

