Leftism, mental health, and visual presentation confirmed

Septum/genital piercings = leftist, mouth/arm tattoos = crazy

So we did another study of leftism, mental health and visual presentation:

• Hu, M.,& Kirkegaard, E. O. W.(2026). Left-wing ideology, mental health and body modifications. Journal of Open Inquiry in the Behavioral Sciences, 5(1).

Recent research has identified a recurring association between left-wing political ideology and poorer mental health. These findings show both reduced positive well-being (e.g., life satisfaction) and increased negative symptoms (e.g., depression, anxiety). We administered 76 mental health and 41 political ideology items to a sample of 978 fairly representative American adults recruited via the Prolific data platform. Overall, we found that every aspect of mental health correlated negatively with overall leftism (r’s for 18 diagnoses = -0.20, last 2 weeks symptoms = -0.14, MMPI-subset = -0.17, life satisfaction = -0.15, all p’s < .001). Diagnoses were the primary predictor of leftism in multivariate models. This relationship was not explained by measurement bias, as invariance testing revealed only minimal, counter-balancing item bias. Furthermore, we expanded this network by incorporating behavioral markers, finding that body modifications (e.g., unnatural hair color, tattoos) showed weak-to-modest associations with both left-wing ideology and mental health diagnoses.

The purpose of the study was mainly to check the measurement invariance of the relationship, since many people had doubted this. Perhaps leftists are just more likely to see therapy or maybe they fill out questionnaires differently. For this reason, we went a bit overboard with the mental health measurement having 76 questions, 18 concerning specific diagnoses and the remaining the more commonly used self-report questions about various aspects. Politics was measured using 41 questions concerning various current thing political questions for Americans, and scored just using the 1-factor model. (Yes, one can extract other dimensions but this one is dominant.) General results:

The various scales called “p” are mental health reversed (worse) based on different approaches. Symptoms is all the self-report scales items combined, diag = diagnoses count, MMPI = items from MMPI (yes/no format), last2weeks (typical format used in surveys), satisfaction (positively phrased questions about life satisfaction). The rightmost column shows that leftism correlates positively with every variable except for age. Given these demographic associations (age, female), one may want to try a regression model to see if leftism correlates with mental problems merely because it is correlated with age and femaleness:

The answer is no, not only, but maybe in part. Diagnoses correlates 0.20 with leftism but 0.16 controlled for age, sex, US-born, and race (though the CI overlaps with 0.20). More interesting is that the models that include both self-report measures and diagnoses counts, the diagnoses have the signal and the others turn non-significant (but stay positive). With ~1000 people, we can’t say whether diagnoses count mediates the entire effect but possibly. One could even try controlling for self-reported mental problems and see if leftism still predicts diagnoses:

And yes, diagnoses still predict but at about half the strength as the raw link (0.10 vs. 0.20). As a first step into measurement invariance testing, we can check whether the questions that better measure overall psychopathology predict leftism better as well (Jensen’s method):

This was also found to be the case, thus showing that the link is via the general factor (p). One can also try from the opposite side, do the questions that better measure overall leftism correlate more with mental illness?:

The answer is also yes, though the correlations aren’t that impressive. This kind of analysis has a sample size related toward-0 bias, so it is not so easy to say what the hypothetical infinite sample size correlation would be, but it would be higher. Fun fact was that the best political question for predicting mental illness was “Western civilization is uniquely evil”, a combined self-hatred and leftism question for Whites.

Next up we also used the more standard DIF (differential item functioning) approach:

We didn’t find much evidence of directional bias in the measurement, no matter how the mental health questions were scored (separately by scale, mixed). There were many biased items but they were roughly evenly balanced, as is typical.

From the perspective of stereotype accuracy, one can also check whether the various bodily modifications have independent signal for predicting either leftism or mental illness:

It turns out that controlling for age, sex, and race, tattoos and piercings don’t predict leftism, but unnatural hair color does, as does diagnoses. However, for predicting mental diagnoses, tattoos work while piercings and unnatural hair color does not, with or without including leftism as a predictor. Thus, the adept stereotyper would have to remember that unnatural hair color is particularly indicative of leftism, while tattoos are particularly indicative of poor mental health.

One issue with the piercing variable is that women have a lot of earrings compared to men, and this doesn’t relate much to anything aside from being a woman:

We also see the usual far-left effect of political ideology, as opposed to a clean linear trend:

Though given the sample size and sex interaction, it was strangely only seen in men.

Leftism by piercing type was amusing:

It is particularly genital and septum (ugly nose) piercings that associate with leftism, the latter which is in line with popular memes. An entire standard deviation difference between those with and without! The tattoos that predict diagnoses were in particular places on the body: arms (hard to hide?), mouth (over 1 SD effect) and “other”. These results hold when controlling for the other piercings and tattoo locations, as well as demographics.

The data are public if you want to try some other ideas. From an academic-political question, I guess this publication also provides another study to cite if one doesn’t want to cite our now retracted Finnish study. The findings are about the same.