Is Testosterone Really Linked to Aggression? What Does the Science Say

About Us

Is Testosterone Really Linked to Aggression? What Does the Science Say

The neuroscience underlying the testosterone-aggression relationship involves complex interactions between hormone levels, brain regions, and neurotransmitter systems. Furthermore, the relationship might also be bidirectional, meaning aggressive behaviour could lead to higher testosterone levels, as seen in animal studies . The discussion encompasses theories such as the challenge hypothesis and parental investment theory, which offer evolutionary explanations for the role of testosterone in aggressive behaviors. Examining the broader social context, this section discusses how testosterone-mediated effects on social dominance may contribute to aggressive behavior. This subsection analyzes research exploring the intricate interplay between testosterone and cortisol levels and their joint influence on aggressive behavior. Studies utilizing survey data, behavioral observations, or self-report measures are discussed to provide a comprehensive overview of the evidence linking testosterone levels to aggression. The interplay between testosterone and neurotransmitters forms a crucial link in understanding the hormone’s influence on aggressive behavior.
However, they can also be used as an experimental treatment to temporarily maximize T production within an individual’s current capabilities or reactive scope. Another direct approach is to use a more fleeting treatment, such as injections with T (Rutkowska et al. 2005), or less invasive methods like fast-acting hormone gels (Vitousek et al. 2018b) and hormone-laced food (Remage-Healey and Bass 2006; Heimovics et al. 2015). Studies using GnRH challenges have shown that an individual’s ability to elevate T is correlated with proxies of condition or quality, pad.geolab.space such as body mass or ornamentation (Millesi et al. 2002; McGlothlin et al. 2008; George et al. 2021). Notably, though, much of the process by which a social challenge alters T secretion remains a black box (Ball and Balthazart 2020).
We have been systematically examining the relationship between T and aggression in female tree swallows (Tachycineta bicolor), an obligate secondary cavity-nesting songbird species that readily breeds in artificial cavities (i.e., nestboxes) across North America. Presumably individual condition also may change over time, and further investigation of these within-individual perspectives will advance our understanding of the causal relationship between T and aggression, and how these relationships affect performance in nature. Along these lines, a recent meta-analysis found some indication that fitness effects of hormone implants, including T, depend upon starting hormone levels (Bonier and Cox 2020). Applying this phenomenon to the context of social challenges, the observation that T often decreases after a simulated territorial challenge could in fact be evidence for, rather than against, T’s involvement in mediating the behavioral response. Similarly, if T is metabolized into inactive forms after hormone-receptor binding, we might expect to see lower T among animals in which T has recently activated behavioral changes. Collectively, these processes may affect our ability as researchers to see socially induced changes in T secretion when analyzed among individuals. It is also reasonable, if not parsimonious, to expect animals of different quality or condition to have different degrees of social responsiveness, such that some individuals’ T secretion changes more quickly or with greater magnitude (i.e., animals differ in their reactive scope).
The first study in prisoners was conducted in 1972, soon after the feasibility of testosterone estimation, by Kreutz and Rosel, who found that prisoners who had committed violent crimes during their adolescence had higher testosterone levels (13). Several field studies have also shown that testosterone levels increase during the aggressive phases of sports games. Atavistic residues of aggressive behavior prevailing in animal life, determined by testosterone, remain attenuated in man and suppressed through familial and social inhibitions. “It has been suggested that the antisocial behaviors related to high testosterone are a function of the manner by which dominance is maintained in these groups,” says Robert Josephs of the University of Texas at Austin. “Historically, researchers expected an increase in testosterone levels to inevitably lead to more aggression, and this didn’t reliably occur,” says Frank McAndrew, a professor of psychology at Knox College in Galesburg, Ill.
One psychologist, James Dabbs of Georgia State University in Atlanta, made a career out of conducting studies connecting testosterone to every kind of lifestyle imaginable. In other words, if researchers were to study other groups of folks, say the rich and famous, they might discover that testosterone is connected not to violence, but to who drives the biggest SUV or has the nicest lawn. Indeed, the latest research about buy testosterone online no prescription and aggression indicates that there’s only a weak connection between the two. Hormones don’t necessarily make men violent, but they do cause them to seek social dominance The action of testosterone on the brain begins in the embryonic stage. Like any surgical procedure, neutering carries some risks and potential side effects, including pain, swelling, and infection at the surgical site.
The close link between aggression and testosterone store is not surprising, given that males of many species fight over access to fertile females, but the connection is complex. In male mice the scent of another male’s urine, which contains the breakdown products of testosterone, elicits intense aggressive responses. Many vertebrate brain structures involved in the control of aggression are richly supplied with receptors that bind with hormones produced in the endocrine system, in particular with steroid hormones produced by the gonads. In adult males neuroimaging techniques that have permitted visualization of brain functions have shown that testosterone activates the amygdala enhancing its emotional activity and its resistance to prefrontal restraining control. Even earlier at the DNA level, the number of CAG repeats in the genes of the androgen receptors appear to play a role in the expression of aggressive behavior.
First, we reiterate past work showing that the mechanisms linking T and aggression vary across timescales, such that longer-term feedbacks do not necessarily occur at shorter timescales (Goymann et al. 2007; Goymann 2009). Thus, it is clear that T and aggression may not co-vary at every timescale or every level of analysis, but T and aggression may still be mechanistically linked. We found mixed support for predictions about among-individual variation and within-individual variation at shorter, more immediate timescales. However, we have shown that temporary GnRH-induced T elevations did not negatively impact parental care in male tree swallows (George et al. 2021), even though T treatment itself negatively impacts parental care in females (Rosvall 2013). We do not yet know if this is the case, and empirically testing this idea has logistical hurdles, but greater attention to these sorts of within- vs. among-individual patterns will be crucial in the future. However, we suspect this to be true, considering our observations that T is positively correlated with aggression at baseline (Lipshutz and Rosvall 2021) but negatively correlated after STI (George et al. 2022). This aggression-sensitive gene network included steroidogenic acute regulatory protein, CYP11A1, P450scc, and adrenodoxin, all of which are key players in producing steroids from cholesterol.
Stage-to-stage variation in aggression directed at a staged territorial intruder was also higher during territorial establishment when T levels are higher, and lower during the chick period when T levels are low (Bentz et al. 2019b). Territorial females with higher circulating T levels spent more time attacking a taxidermic decoy during a simulated territorial intrusion at their nest boxes, whereas lower T females spent less time attacking (Lipshutz and Rosvall 2021). Compared to controls, females given T implants behave more aggressively toward a same-sex decoy (Rosvall 2013).
Nevertheless, testosterone is not static but instead fluctuates in response to cues of challenge in the environment, and these challenge-induced fluctuations may more strongly regulate situation-specific aggressive behaviour. Not all aggressive behaviour is caused by testosterone. The meta-analysis supports a weak but positive link between testosterone and aggression in 83% of the results, regardless of the time of day . Aggression was defined broadly, including competition, self-reported aggression, criminal records, and ratings of aggressive behaviour from close ones . The study analysed 45 studies with 9,760 participants, combining data to identify trends . Additionally, exploring the moderating and mediating variables that influence this relationship will contribute to a more nuanced understanding.