The science behind stress: what’s really going on in your body?

Why does stress exist in the first place?

We talk about stress like it’s a flaw. Something to manage, battle, or just grin and bear. 

But stress isn’t a mistake in the system - it is the system. A natural, even crucial part of the human experience. Think of it like your very own built-in alarm, wired through your brain and body, designed to keep you alive.

To mark the start of Stress Awareness Month, we’re interested in:

• What stress actually is 
• Why it happens
• What it does to your organs, hormones, and senses in real-time. 
• How that response can shift from protective to problematic - especially if and when it becomes chronic
• And finally, how a UK medical cannabis prescription may help regulate stress responses in patients with one of the many conditions it can be legally prescribed for.

What’s the difference between acute and chronic stress?

Not all stress is created equal. It can be broken down into two broad categories.

Recognising the difference is key. 

• Acute stress helps you survive. 
• Chronic stress slowly strips away your ability to perform at your peak, or worse.

Acute stress

Acute stress is the body's way of rising to the occasion. It’s what kicks in when you slam on the brakes, speak in public, or feel your heart race before an interview. These short bursts are designed to help you react quickly, focus sharply, and get out of danger. 

Once the moment passes, the body resets - or that’s what is supposed to happen, but we all know that isn't always the case.

Chronic stress

Chronic stress is something else entirely. It's what happens when the same alarm keeps ringing long after the threat has passed. Over time, that constant background pressure builds up. It can affect everything from your sleep and digestion to your mental health, immune function and response, and memory retention and recall.

This is where stress stops being useful and starts becoming a problem. 

It pulls your body out of balance and keeps it there. The technical term for that wear and tear is allostatic load - the accumulated toll of your systems being on red alert all the time.

What happens inside the body during stress?

When you feel stressed, it’s not just in your head. The signal runs deep.

It all starts in the brain - first through the amygdala (which processes what our senses tell us) and then to the hypothalamus if danger is present. 

This tiny command centre sends a message down the line to your adrenal glands, prompting the release of adrenaline and cortisol: the body’s key stress hormones. This is the HPA axis in action (hypothalamic-pituitary-adrenal), and it runs the show whenever a threat is perceived.

The moment it switches on, your body prepares to act.

The physical symptoms of stress

Your heart races. Breathing quickens. Muscles tighten. Blood flow shifts away from digestion towards your limbs. Your pupils widen and your focus narrows. This is the classic “fight-or-flight” response, and it’s been keeping us alive since before the dawn of humankind.

But not all symptoms are so obviously tied to threat. 

Stress can show up as tension headaches, sleep disruption, digestive issues, or skin reactions like stress rash, hives, or eczema. These are common physical symptoms of stress, though they’re often overlooked or misinterpreted.

When the stress response is acute, your body resets quickly. But if the pressure sticks around, these changes start to take a toll.

Why does long-term stress take such a toll?

Although stress primes the body to act, to help us escape threats and restore the balance once the danger passes, the modern world rarely grants that exit. Instead, it leaves the system half-cocked: ready to fly, but with stormy skies above and below.

This is because the longer the stress response remains active, the more it begins to work against the very systems it was built to protect.

What chronic stress does to the body and brain

Cortisol isn’t just a ‘stress hormone’. 

It controls energy levels, supports the immune response, and keeps inflammation in check. But when cortisol stays elevated for too long, it reverses course. It begins to suppress immune function, disrupt sleep, and alter metabolism. You slowly become more reactive, less resilient, and increasingly depleted.

Many of the symptoms associated with chronic stress are easy to dismiss or pass off as just your everyday wear and tear - tiredness, forgetfulness, digestive issues, and anxiety. But each one is a signal of something deeper going a little haywire - of a body trying to function while stuck in survival mode.

Neurologically, the effects are just as profound. 

The amygdala grows more and more sensitive (and reactive) to perceived threats, real or not. The hippocampus, which helps regulate memory and emotion, starts to shrink. Thinking clearly can quickly become a real issue. And with these changes comes the potential for you to lose the ability to properly distinguish between what requires immediate action and what you can simply let pass.

This is the cost of long-term stress. It is not always visible, but it is quietly, persistently real.

How does cannabis interact with the stress response?

The body isn’t just wired to react, it’s also built to recover. And in 1988, scientists discovered one of the key systems behind that process - the endocannabinoid system, or ECS.

If your stress response is the car, and adrenaline and cortisol are the petrol and accelerator, the ECS is the traffic light. It helps your body know when to go, when to slow, and when to stop. 

This system runs quietly in the background, regulating everything from mood and memory to appetite, immune function, hormonal balance… The list is too long to cover here, but the ECS touches almost every part of how we experience internal stability.

When you’re under threat, the ECS helps keep the stress response in check. It can modulate the release of cortisol, dampen inflammation, and support emotional recovery once the moment has passed. But when the stress is constant — chronic and unrelenting — the ECS itself can start to falter. The lights stop working properly. The body loses its rhythm.

The role of cannabinoids

This is where cannabis may play a role. Cannabinoids like CBD and THC interact with the ECS in different ways, helping to restore signalling where it’s been disrupted.

CBD, for instance, has been shown to influence cortisol levels and reduce over-activation in brain regions like the amygdala. THC, in low doses, can reduce hyperarousal and promote calm in some individuals. You can think of cannabinoids as external traffic engineers — not replacing the system, but helping restore its rhythm when it’s out of sync.

Medical cannabis is not some type of magic cure, and it is not a ‘first line’ treatment option here in the UK. But, for some patients suffering from chronic stress, it can support the shift out of ‘fight-or-flight’ and back into a state of physiological balance. 

For those among us living with chronic stress, it should always be seen as one small part of a holistic treatment plan - one that includes movement, rest, therapy, self-work, and any number of other supportive therapy options.

Feeling the strain?

If you’re dealing with stress, you’re not alone - and you don’t have to try and figure it out in all by yourself. We all go through periods of heavy stress, and it is a common secondary symptom attached to many of the health issues that medical cannabis can be legally prescribed for here in the UK.

Releaf offers access to a quick, simple, and free medical cannabis eligibility checker that can help you find out if medical cannabis might be a suitable option for you. It takes just 20 seconds to complete, and from there, you will have a much clearer understanding of if you may be eligible for a UK medical cannabis prescription. 

Stress is complex. The right support should be straightforward, and that’s exactly what we offer here at Releaf. 

Want to learn more? 

Check out our full New Patient blog series, where we cover everything from the difference between medical cannabis and recreational weed to medical cannabis side effects, THC vs CBD, and how long medical cannabis takes to work.