As our medical understanding of hormones has expanded, it has trickled down into popular culture that hormones play significant roles not only in health but also in behavior. Current medical knowledge is fairly advanced when it comes to understanding how a single hormone works in isolation, but much more limited when it comes to how multiple hormones interact and how they vary across individuals.
Because of this, it has become popular to label individual hormones as responsible for single functions: testosterone is considered the “masculine” one, oxytocin is associated with love and affection, dopamine with thrills and reward, and serotonin with sleep. In reality, all of these processes are far more complex than a one-to-one correlation with a single hormone. Still, for the sake of simplification, popular culture often reduces these nuanced systems to a handful of major hormones.
One of the most popular hormones to blame is cortisol—the so-called “stress hormone.” Since no one likes stress, and most people feel stressed frequently, it’s easy to explain stress-related issues like weight gain, fatigue, or illness in terms of cortisol, reframing stress as a medical condition rather than a social or environmental one. However, popular ideas about cortisol are filled with misunderstandings, often amplified by supplement marketing.
Cortisol is one of many hormones that rise during the body’s fight-or-flight response. While it does spike during moments of stress, cortisol naturally fluctuates throughout the day and may have little to do with stress at all. It helps regulate daily rhythms, peaking in the morning and dipping by mid-afternoon (often during that “3 p.m. slump”). Cortisol levels also rise during menopause and in conditions such as PCOS. Importantly, lowering cortisol in isolation does not automatically reduce stress-related symptoms like weight gain or puffiness in the face.
It’s common to hear an analogy that cortisol was once useful for helping our ancestors run from lions, but today it gets mistakenly triggered by emails. The reality is more complicated: daily stress isn’t simply a misfiring of an ancient system—it carries real, cumulative physical consequences.
In the 1970s, a now-famous study of rhesus monkeys showed that low-status or socially bullied monkeys consistently gained weight. This research shifted how scientists view chronic, low-grade stress. Later studies confirmed that subordinate monkeys have higher cortisol levels, which are associated with increased appetite and greater visceral fat storage. Still, cortisol is only part of the picture; reducing cortisol levels alone does not eliminate the external stressors that trigger its rise.
Robert Sapolsky’s book Behave dedicates an entire chapter to stress and cortisol. He emphasizes that sustained stress is far more damaging than brief, intense stress. Cortisol is designed for short bursts—like escaping a predator—not days or weeks of elevation. This explains why “good” spikes in cortisol, such as those triggered by exercise or even an action movie, can have beneficial effects.
Sapolsky also highlights that much of hormone research has been conducted through a male-dominated medical lens. The classic “fight-or-flight” model may not reflect women’s typical stress response. For women, cortisol spikes may more often lead to a “tend-and-befriend” response, focusing on care and social bonding rather than combat or escape. Psychology has introduced some additional terms for survival responses—like “fawning” or “mirroring”—that may be more common, especially for women.
Ultimately, Sapolsky notes: “The core of psychological stress is loss of control and predictability.” As our world becomes more complex and unpredictable, it’s not surprising that many people live with elevated cortisol levels. However, we tend to think of fixing or healing our cortisol levels to feel better instead of adjusting our lifestyles.
