Are Dark Tetrad personality traits associated with baseline, reactive, or prenatal testosterone? A systematic review and meta-analysis of the literature

The Dark Tetrad of personality (narcissism, Machiavellianism, psychopathy, and everyday sadism) is a set of socially undesirable traits potentially linked to both organizational (i.e., prenatal, long-term) and activational (i.e., postnatal, short-term) effects of testosterone. This systematic review and meta-analysis of the literature aimed to re-evaluate previously published data on Dark Tetrad traits and baseline testosterone, reactive (post-task) testosterone, and digit ratio 2D:4D as a proxy for prenatal testosterone exposure. We identified 19 studies on circulating testosterone and 10 studies on digit ratio 2D:4D in non-clinical populations. Our analyses revealed: 1) small but significant positive associations between baseline testosterone and Machiavellianism as well as primary and secondary psychopathy, (the association with grandiose narcissism was weaker and non-significant); 2) a tendency for a small and positive association between reactive testosterone and grandiose narcissism, (the associations with primary and secondary psychopathy were non-significant and no data on other Dark traits were available); 3) a more masculine digit ratio 2D:4D, particularly in the right hand, was significantly associated with grandiose narcissism, Machiavellianism, and secondary, but not primary, psychopathy. These findings suggest that testosterone is associated with Dark Tetrad traits in trait-specific and timing-specific ways, with activational effects potentially linked to Machiavellianism and to primary and secondary psychopathy, and organizational effects potentially linked to grandiose narcissism, Machiavellianism, and secondary psychopathy. More data are needed on vulnerable narcissism and everyday sadism in relation to testosterone.