A Legacy of Stress: A Modern Critique of Hans Selye’s Ground-breaking Research

Talking to people these days about stress and they often give the impression that the “science is settled”. Not only is that attitude not scientific, but when it comes to stress it's a long way from the truth. Indeed, most of the people I talked to seemed to think stress is caused by a neurotransmitter called cortisol, which is even further from the truth. As a result, this article is intended to give an overview of the history of our understanding of stress and some ideas as to where we are today.

To start with let me explain why cortisol is focused upon. It goes back to the 1930s and a very clever endocrinologist called Hans Selye. These days Han Selye is often hailed as the "father of stress research," and has profoundly influenced our understanding of how organisms respond to stressors. His concept of General Adaptation Syndrome (GAS), introduced in 1936, outlined a three-stage model - alarm, resistance, and exhaustion - that described the physiological progression of stress responses. Despite the undeniable significance of his contributions, critical examination of Selye's theories highlights significant limitations that modern research has sought to address.

Let’s explore the key critiques and lasting impacts of his work from a more modern and informed perspective in order to understand how our perception of stress has evolved.

One of the most notable critiques of Selye’s model is its focus on physiological processes to the exclusion of psychological factors. Stress, as defined by Selye, was a non-specific biological response to any demand. While this definition was revolutionary for its time, it left no room for cognitive appraisal, perception, or emotional processing - all of which are now recognised as significant to the human stress experience.

One of the alternate models which sprang out of this valid criticism is the Transactional Model of stress. This was proposed by Richard Lazarus and Susan Folkman in 1984. It posits that stress is highly subjective, dependent on how individuals interpret and both consciously and unconsciously cope with stressors. According to their framework, what constitutes a significant stressor for one person can be trivial to another. This emphasis on personal perception as an aspect of stress, offers a more nuanced understanding than Selye’s universal biological mechanism.

Looking at it in another way, Selye’s GAS model presents stress responses as a linear progression through fixed stages:

1. The alarm reaction when the body detects a threat.
2. The resistance phase where coping mechanisms kick in.
3. The exhaustion stage if the stress persists too long.

However, this rigid structure does not fully reflect the complexity of our stress responses. Much of modern research recognises there are non-linear responses, where individuals may return to a baseline state without progressing to exhaustion, or even experience fluctuating cycles of stress and recovery. Furthermore, chronic stress does not always result in exhaustion as Selye proposed - its effects can vary significantly among individuals.

This brings us to Bruce McEwen’s Allostatic Load Model which provides a more dynamic interpretation, describing how repeated stress cycles can wear down the body differently, depending on individual resilience and recovery capacity.

A further criticism is that much of Selye’s experimental work was conducted on rats, exposing them to physical stressors like heat and cold. While this approach was instrumental in mapping the physiological pathways of stress, it clearly poses limitations when applied to human experiences. Unlike rats, human stress responses are influenced by cognitive, psychological, emotional, and social factors. Contextual and subjective elements, such as emotional support or prior experiences, are critical in human stress management but were beyond the scope of Selye’s animal-based research.

Adding to all this are the more recent investigations into Psychoneuroimmunology and behavioural health. These emphasise the interplay between mental states and physical stress outcomes - a connection that Selye's framework did not directly address.

Selye famously described stress as "the non-specific response of the body to any demand". While this broad definition undoubtedly helped popularise the concept, it also introduced significant ambiguity. By categorising all responses under one umbrella, Selye blurred distinctions between various types of stressors (e.g., emotional vs physical) and between what Selye termed positive (eustress) and negative (distress) experiences.

We find that modern researchers have refined this approach, differentiating between beneficial stress that enhances performance and harmful stress that undermines well-being. Cox (1978) has pointed out that stress must be framed as a process involving a stressor, cognitive appraisal, and physiological or behavioural response. This helps by clarifying distinctions that Selye's definition obscured.

A key shortcoming of the GAS model is its assumption of a generalised, universal reaction to stress. Contemporary research has shown that stress responses vary widely, based on personality traits, genetic predispositions, past trauma, and environmental factors. Also that resilience, coping mechanisms, and social support can all significantly influence how individuals experience and recover from stress.

For instance, the Differential Susceptibility Model (Belsky et al) demonstrates that some individuals are more biologically sensitive to adverse environments, while others are more resilient. This concept aligns with findings in epigenetics and mental health research, further challenging the one-size-fits-all notion presented by Selye.

Despite its limitations, Selye’s work remains foundational. His exploration of the hormonal and physiological impacts of stress, including the role of cortisol and adrenal responses, paved the way for modern studies on stress-related illnesses, such as cardiovascular disease and immune suppression. His introduction of the terms eustress and distress offered a critical insight into how not all stress is harmful - a concept widely embraced in performance psychology and workplace stress management.

In conclusion, Hans Selye’s research on stress was groundbreaking, but it should be regarded as an entry point into a much broader and more complex field. His General Adaptation Syndrome model and its endocrinological foundations, while influential, requires supplementation by contemporary models that integrate cognitive, social, and individual factors. By recognising these advancements, we honour Selye’s legacy while embracing the evolving science of stress.